As promised, today I will write an article on how to make a RAID array from two disks. Who has not read about that, read the link. So, these arrays are able to solve the most important problems in the system. As an example, we can cite the fact that with the help of arrays we can protect important data in the event of a hard disk failure and increase the speed of the system. In the previous article about RAID arrays, I said that this technology is used mainly on servers in various companies, but nothing prevents us from using it on home computers, especially since this does not require much (motherboard that supports arrays and two drives of the same characteristics).
So let's start creating RAID arrays. I must say right away that you need to transfer all the most important data to another medium, because the disks will be cleared during the creation process.
How to create a RAID array using the built-in controller?
If your motherboard supports the creation of raids, then read this manual. We will work on the basis of ASUS motherboards with support, but the principle of creation is almost the same everywhere. Go.
First we need, in ASUS motherboards they usually press the key DEL... Now you need to go to the section where the parameters for the SATA controller are located.
Usually, the position is switched to ACHI, but you have to put it in position RAID... As I said in the previous article, your disks must be completely identical, absolutely in ALL parameters. Now, as usual, we save the settings and restart the computer.
During the computer restart, that is, before the system boots, you need to press the combination CTRL-I or CTRL-Fsometimes this is not required.
In our experiment with an ASUS board, we see the following window with the following parameters:
- View Drive Assignments - the parameter allows you to see the disks that we can use in creating a RAID array.
- LD View / LD Define Menu - this parameter shows already created arrays.
- Delete LD Menu - here I think it's clear. Removing the created arrays.
- Controller Configuration - various settings.
In our case, we select item 2. Press the 2 key on the keyboard and get into the next window.
Here, as already mentioned, there are already created RAIDs. To view the settings, just press the key Enter... Combinations Ctrl + V allows you to see disks that are outside the arrays. Using the keys Ctrl + C we can create new arrays. We need to create an array, therefore, we press Ctrl + C.
In the next window, we will see a menu in which raids will be created, it is at the top. Disks that are not yet used as raids are at the bottom. We can toggle the parameters with a space, and the items of these parameters with arrows on the keyboard.
Reminder! If you don't remember then RAID 1 we are responsible for duplicating disks, that is, if one fails, then all the information will remain on the second. This creates data security. RAID 0 is responsible for increasing system performance, because the disks work simultaneously, which creates the maximum read and write speed.
In the screenshot above, the parameters for creating RAID 1, but there was nothing special to set there, since the parameters were mostly by default, only the raid type and disks were selected.
As soon as all the necessary parameters are set, press the keys Ctrl + Y.
Then, you can press any key, then the name of the raid will be set by default, or press Ctrl + Y again and specify your name. The second option looks like this:
After that, a warning will appear stating that all data from the disks will be destroyed. If you are sure that you have saved all the necessary data, then click again CTRL + Y.
Next, a window will appear where you will need to select a size for the array, or it will take up all the space on the disks. You can select the entire space, there will be nothing wrong with that. To do this, press any key.
That's all, we have created a RAID array, now we restart the computer.
Now you need to allocate space on the raid and initialize. You can do this in the Disk Management Wizard, which is located along the path: Control Panel — Administration — Computer management — Disk management.
You also need to create partitions and allocate places, but here I think you will not have any problems. Just right-click on an unallocated section and select Create Simple Volume.
Actually, although the article turned out to be voluminous, I painted it rather briefly. Therefore, ask questions in the comments if something is not clear. I will write more articles about RAID arrays, so stay tuned for the site updates.
Sergey Pakhomov
All modern motherboards are equipped with an integrated RAID controller, and top models even have several integrated RAID controllers. How much the integrated RAID controllers are in demand by home users is a separate question. In any case, a modern motherboard provides the user with the ability to create a RAID array from several disks. However, not every home user knows how to create a RAID array, which level of the array to choose, and generally has a poor idea of \u200b\u200bthe pros and cons of using RAID arrays.
History of creation
The term "RAID array" first appeared in 1987, when American researchers Patterson, Gibson and Katz from the University of California, Berkeley, in their article "A Case for Redundant Arrays of Inexpensive Discs, RAID", described how In this way, multiple low-cost hard drives can be combined into a single logical device so that the result is increased system capacity and performance, and the failure of individual drives does not lead to failure of the entire system.
More than 20 years have passed since the publication of this article, but the technology of building RAID arrays has not lost its relevance today. The only thing that has changed since then is the decoding of the RAID acronym. The fact is that initially RAID arrays were not built on cheap disks, so the word Inexpensive was changed to Independent, which was more in line with reality.
Operating principle
So, RAID is a redundant array of independent disks (Redundant Arrays of Independent Discs), which is entrusted with the task of providing fault tolerance and improving performance. Fault tolerance is achieved through redundancy. That is, part of the disk space is allocated for service purposes, becoming inaccessible to the user.
The increase in the performance of the disk subsystem is provided by the simultaneous operation of several disks, and in this sense, the more disks in the array (up to a certain limit), the better.
Disk sharing in an array can be done using either parallel or independent access. With parallel access, disk space is divided into blocks (strips) for data recording. Likewise, the information to be written to the disk is divided into the same blocks. When writing, separate blocks are written to different disks, and several blocks are written to different disks simultaneously, which leads to an increase in performance in write operations. The necessary information is also read in separate blocks simultaneously from several disks, which also contributes to an increase in performance in proportion to the number of disks in the array.
It should be noted that the parallel access model is implemented only if the size of the data write request is larger than the size of the block itself. Otherwise, it is almost impossible to write multiple blocks in parallel. Imagine a situation where the size of an individual block is 8KB, and the size of a write request is 64KB. In this case, the original information is cut into eight blocks of 8 KB each. If you have a four-disk array, you can write four blocks, or 32KB, at a time. Obviously, in the considered example, the write speed and read speed will be four times higher than when using a single disc. This is true only for an ideal situation, but the request size is not always a multiple of the block size and the number of disks in the array.
If the size of the recorded data is less than the block size, then a fundamentally different model is implemented - independent access. Moreover, this model can also be used when the size of the recorded data is greater than the size of one block. With independent access, all the data of a single request is written to a separate disk, that is, the situation is identical to working with one disk. The advantage of the independent access model is that if multiple write (read) requests are received at the same time, they will all be executed on separate disks independently of each other. This situation is typical, for example, for servers.
According to the different types of access, there are different types of RAID arrays, which are usually characterized by RAID levels. In addition to the type of access, RAID levels differ in the way they are located and redundant information is generated. Redundant information can either be placed on a dedicated disk or shared across all disks. There are many ways to generate this information. The simplest of these is full duplication (100% redundancy), or mirroring. In addition, error correction codes as well as parity calculations are used.
RAID levels
Currently, there are several RAID levels that can be considered standardized - these are RAID 0, RAID 1, RAID 2, RAID 3, RAID 4, RAID 5, and RAID 6.
Various combinations of RAID levels are also used to combine their merits. This is usually a combination of some fault tolerant level and level 0 used to improve performance (RAID 1 + 0, RAID 0 + 1, RAID 50).
Note that all modern RAID controllers support the JBOD (Just a Bench Of Disks) function, which is not intended for creating arrays - it provides the ability to connect individual disks to the RAID controller.
It should be noted that the RAID controllers integrated on motherboards for home PCs do not support all RAID levels. Dual-port RAID controllers support only levels 0 and 1, while RAID controllers with a large number of ports (for example, the 6-port RAID controller integrated into the south bridge of the ICH9R / ICH10R chipset) also support levels 10 and 5.
In addition, if we talk about motherboards based on Intel chipsets, then they also implement the Intel Matrix RAID function, which allows you to create RAID matrices of several levels on several hard drives at the same time, allocating a part of the disk space for each of them.
RAID 0
RAID level 0, strictly speaking, is not a redundant array and therefore does not provide data storage reliability. Nevertheless, this level is actively used in cases where it is necessary to ensure high performance of the disk subsystem. When creating a RAID 0 array, information is split into blocks (sometimes these blocks are called stripes), which are written to separate disks, that is, a system with parallel access is created (if, of course, the block size allows it). With the ability to concurrently I / O from multiple drives, RAID 0 provides the fastest transfer rates and maximum disk space utilization since it does not require storage space for checksums. The implementation of this level is very simple. RAID 0 is mainly used in areas where fast transfer of large amounts of data is required.
RAID 1 (Mirrored disk)
RAID Level 1 is a 100 percent redundant array of two drives. That is, the data is simply completely duplicated (mirrored), due to which a very high level of reliability (as well as cost) is achieved. Note that implementing Level 1 does not require pre-partitioning disks and data into blocks. In the simplest case, two drives contain the same information and are one logical drive. If one disk fails, its functions are performed by another (which is absolutely transparent to the user). The array is restored by simple copying. In addition, this level doubles the speed of information reading, since this operation can be performed simultaneously from two disks. This information storage scheme is used mainly in cases where the cost of data security is much higher than the cost of implementing the storage system.
RAID 5
RAID 5 is a fault-tolerant disk array with distributed checksum storage. When writing, the data stream is divided into blocks (stripes) at the byte level and simultaneously written to all disks in the array in a circular order.
Suppose the array contains n disks, and the stripe size d... For each portion of n-1 stripes checksum is calculated p.
Stripe d1 written to the first disk, stripe d2 - on the second and so on up to the stripe dn-1which is written to ( n-1) th drive. Further on n-th disk checksum is written pn, and the process is cyclically repeated from the first disk on which the stripe is written dn.
Recording process (n-1) stripes and their checksum are produced simultaneously for all n disks.
The checksum is calculated using a bitwise exclusive OR (XOR) operation on the data blocks being written. So, if there is n hard drives, d - data block (stripe), the checksum is calculated using the following formula:
pn \u003d d1+d2+ ... + d1-1.
If any disk fails, the data on it can be recovered from the control data and from the data remaining on the healthy disks.
As an illustration, consider blocks of four bits. Suppose there are only five drives for storing data and writing checksums. If there is a sequence of bits 1101 0011 1100 1011, divided into blocks of four bits, then to calculate the checksum, you must perform the following bitwise operation:
1101 + 0011 + 1100 + 1011 = 1001.
Thus, the checksum written to the fifth disc is 1001.
If one of the disks, for example the fourth, fails, then the block d4 \u003d 1100 will be unavailable when read. However, its value can be easily restored from the checksum and from the values \u200b\u200bof the remaining blocks using the same "exclusive OR" operation:
d4 \u003d d1+d2+d4+p5.
In our example, we get:
d4 \u003d (1101) + (0011) + (1100) + (1011) = 1001.
In the case of RAID 5, all the disks in the array are the same size, but the total capacity of the disk subsystem available for writing becomes less than exactly one disk. For example, if five disks are 100 GB, then the actual size of the array is 400 GB because 100 GB is allocated for audit information.
RAID 5 can be built on three or more hard drives. As the number of hard drives in an array increases, its redundancy decreases.
RAID 5 has an independent access architecture that allows multiple reads or writes to be performed simultaneously
RAID 10
RAID 10 is a combination of levels 0 and 1. A minimum of four drives are required for this level. In a RAID 10 array of four disks, they are paired together into arrays of level 0, and both of these arrays are combined as logical drives into an array of level 1. Another approach is also possible: initially, the disks are combined into mirrored arrays of level 1, and then logical drives based on these arrays - to an array of level 0.
Intel Matrix RAID
The considered RAID-arrays of levels 5 and 1 are rarely used at home, which is primarily due to the high cost of such solutions. The most commonly used for home PCs is a level 0 array on two disks. As we have already noted, RAID level 0 does not provide data storage security, and therefore end users are faced with a choice: to create a fast, but not reliable data storage, RAID level 0, or, doubling the cost of disk space, - RAID- a Tier 1 array that provides data reliability without significant performance gains.
To address this daunting challenge, Intel developed Intel Matrix Storage Technology, which combines the benefits of Tier 0 and Tier 1 arrays on just two physical disks. And in order to emphasize that in this case we are talking not just about a RAID-array, but about an array combining both physical and logical disks, the technology name uses the word "matrix" instead of the word "array".
So what is a dual-drive RAID array with Intel Matrix Storage Technology? The main idea is that if there are several hard drives in the system and a motherboard with an Intel chipset that supports Intel Matrix Storage technology, it is possible to divide the disk space into several parts, each of which will function as a separate RAID array.
Let's take a look at a simple example of a RAID matrix consisting of two 120 GB drives. Any of the disks can be split into two logical disks, for example, 40 GB and 80 GB. Further, two logical drives of the same size (for example, 40 GB each) can be combined into a RAID level 1 matrix, and the remaining logical drives into a RAID level 0 matrix.
In principle, using two physical disks, you can also create only one or two RAID 0 matrices, but it is impossible to get only level 1 matrices. That is, if the system has only two disks, then Intel Matrix Storage technology allows you to create the following types of RAID matrices:
- one matrix of level 0;
- two matrices of level 0;
- level 0 matrix and level 1 matrix.
If the system has three hard disks, then the following types of RAID matrices can be created:
- one matrix of level 0;
- one level 5 matrix;
- two matrices of level 0;
- two matrices of level 5;
- a level 0 matrix and a level 5 matrix.
If the system has four hard drives, then it is additionally possible to create a RAID 10 matrix, as well as combinations of level 10 and level 0 or 5.
Almost everyone knows the proverb "Until the thunder breaks out, the man does not cross himself". It is vital: until this or that problem touches the user closely, he will not even think about it. The power supply died and took a couple of devices with him - the user rushes to look for articles on the relevant topic about tasty and healthy food. The processor burned out or began to glitch due to overheating - in the "Chosen" there are a couple of links to the spreading branches of the forums where they discuss CPU cooling.
It's the same story with hard drives: as soon as another screw, crunching goodbye with its heads, leaves our mortal world, the owner of the PC begins to fuss to ensure that the life of the drive improves. But even the most sophisticated cooler cannot guarantee a long and happy life for a disk. The service life of the drive is influenced by many factors: manufacturing defects, and an accidental kick of the case with a foot (especially if the body is somewhere on the floor), and dust that has passed through filters, and high-voltage noise sent by the power supply ... There is only one way out - backup information, and if you need a backup on the go, then it's time to build a RAID array, since today almost every motherboard has some kind of RAID controller.
At this point we will stop and take a short excursion into the history and theory of RAID arrays. The abbreviation RAID itself stands for Redundant Array of Independent Disks (Redundant Array of Independent Disks). Previously, inexpensive was used instead of independent, but over time this definition has lost its relevance: almost all disk drives have become inexpensive.
The history of RAID began in 1987, when the article "Redundant Array Enclosures from Cheap Disks (RAID)" was published by comrades Peterson, Gibson, and Katz. The article described the technology of combining several conventional disks into an array to obtain a faster and more reliable drive. Also, the authors of the material told readers about several types of arrays - from RAID-1 to RAID-5. Subsequently, a zero-level RAID array was added to the arrays described almost twenty years ago, and it gained popularity. So what are all these RAID-x? What is their essence? Why are they called redundant? This is what we will try to understand.
In very simple terms, RAID is such a thing that allows the operating system to not know how many disks are installed in the computer. Combining hard drives into a RAID array is the opposite of splitting a single space into logical disks: we form one logical drive based on several physical ones. In order to do this, we need either the appropriate software (we will not even talk about this option - this is an unnecessary thing), or a RAID controller built into the motherboard, or a separate one inserted into a PCI or PCI Express slot. It is the controller that combines the disks into an array, and the operating system no longer works with the HDD, but with the controller, which does not tell it anything unnecessary. But there are a great many options for combining several disks into one, more precisely, about ten.
What are RAID types?
The simplest one is JBOD (Just a Bunch of Disks). Two hard drives are glued into one sequentially, information is written first to one, and then to another disk without splitting it into pieces and blocks. Of two 200 GB drives, we make one of 400 GB, which works at almost the same, but in reality, at a slightly lower speed as each of the two drives.
JBOD is a special case of a zero-level array, RAID-0. There is also another variant of the name of arrays of this level - stripe, the full name is Striped Disk Array without Fault Tolerance. This option also involves combining n disks into one with a volume increased by n times, but the disks are combined not sequentially, but in parallel, and information is written on them in blocks (the block size is set by the user when forming a RAID array).
That is, if you need to write a sequence of numbers 123456 to two drives included in the RAID-0 array, the controller will divide this chain into two parts - 123 and 456 - and write the first one to one disk, and the second to the other. Each disk can transfer data ... well, let it be at a speed of 50 MB / s, and the total speed of two disks, data from which are taken in parallel, is 100 MB / s. Thus, the speed of working with data should increase n times (in reality, of course, the increase in speed is less, since no one canceled the losses for searching for data and for transmitting them over the bus). But this increase is given for a reason: if at least one disk fails, information from the entire array is lost.
Level 0 RAID. Data is split into blocks and scattered across disks. No parity or redundancy.
That is, there is no redundancy and no redundancy at all. This array can be considered a RAID array only conditionally; nevertheless, it is very popular. Few people think about reliability, because you can't measure it with benchmarks, but everyone understands the language of megabytes per second. This is neither bad nor good, just such a phenomenon exists. Below we will talk about how to eat fish and keep it reliable. Recovering a RAID-0 after a failure
By the way, an additional minus of the stripe array is its non-portability. I do not mean that he does not tolerate certain types of food or, for example, hosts poorly. He doesn't give a damn about that, but moving the array itself somewhere is a whole problem. Even if you bring both disks and controller drivers to a friend to the bargain, it is not a fact that they will be defined as one array and you will be able to use the data. Moreover, there are known cases when a simple connection (without writing anything!) Of stripe disks to a "non-native" (different from the one on which the array was formed) controller corrupted the information in the array. We do not know how urgent this problem is now, with the advent of modern controllers, but we still advise you to be careful.
RAID-array of the first level of four disks. The disks are divided into pairs; the drives inside the pair store the same data.
The first truly "redundant" array (and the first RAID to emerge) was RAID-1. Its second name - mirror (mirror) - explains the principle of operation: all disks allocated for the array are divided into pairs, and information is read and written to both disks at once. It turns out that each of the disks in the array has an exact copy. In such a system, not only the reliability of data storage increases, but also the speed of their reading (you can read from two hard drives at once), although the write speed remains the same as that of one drive.
As you might guess, the volume of such an array will be equal to half the sum of the volumes of all hard drives included in it. The downside of this solution is that you need twice as many hards. But on the other hand, the reliability of this array is actually not even equal to the double reliability of a single disk, but much higher than this value. Failure of two hard drives within ... well, let's say, a day is unlikely, unless, for example, the power supply intervened in the matter. At the same time, any sane person, seeing that one disk in a pair is out of order, will immediately replace it, and even if immediately after that he gives up the ends of the second disk, the information will not go anywhere.
As you can see, both RAID-0 and RAID-1 have their drawbacks. How to get rid of them? If you have at least four hard drives, you can create a RAID 0 + 1 configuration. For this, RAID-1 arrays are combined into a RAID-0 array. Or vice versa, sometimes they create a RAID-1 array from several RAID-0 arrays (the result will be RAID-10, the only advantage of which is a shorter data recovery time in the event of a single disk failure).
The reliability of such a configuration of four hard drives is equal to the reliability of a RAID-1 array, and the speed is actually the same as that of RAID-0 (in reality, it is likely to be slightly lower due to the limited capabilities of the controller). At the same time, the simultaneous failure of two disks does not always mean a complete loss of information: this will only happen if disks containing the same data break, which is unlikely. That is, if four disks are split into pairs 1-2 and 3-4 and the pairs are combined into a RAID-0 array, then only the simultaneous failure of disks 1 and 2 or 3 and 4 will lead to data loss, while in the case of the untimely death of the first and the third, second and fourth, first and fourth or second and third hard drives, the data will remain intact.
However, the main drawback of RAID-10 is the high cost of the drives. Still, the price of four (at least!) Hard drives cannot be called small, especially if the volume of only two of them is really available to us (few people think about reliability and how much it costs, as we have already said). Large (100%) data storage redundancy makes itself felt. All this has led to the fact that in recent years, a variant of the array called RAID-5 has gained popularity. Three disks are required for its implementation. In addition to the information itself, the controller also stores parity blocks on the array drives.
We will not go into the details of the operation of the parity check algorithm, let's just say that it allows, in the event of information loss on one of the disks, to recover it using parity data and live data from other disks. The parity block has the capacity of one physical disk and is evenly distributed across all hard drives in the system so that the loss of any disk allows you to recover information from it using a parity block located on another disk in the array. The information is divided into large blocks and written to the disks one by one, that is, according to the 12-34-56 principle in the case of a three-disk array.
Accordingly, the total volume of such an array is the volume of all disks minus the capacity of one of them. Data recovery, of course, does not happen instantly, but such a system has high performance and a margin of safety at the lowest cost (for a 1000 GB array, six 200 GB disks are needed). However, the performance of such an array will still be lower than the speed of the stripe system: with each write operation, the controller also needs to update the parity index.
RAID-0, RAID-1 and RAID 0 + 1, sometimes even RAID-5 - these levels often exhaust the capabilities of desktop RAID controllers. Higher levels are available only for complex systems based on SCSI hard drives. However, lucky owners of SATA controllers with Matrix RAID support (such controllers are built into the ICH6R and ICH7R south bridges from Intel) can take advantage of RAID-0 and RAID-1 arrays with only two disks, and those who have a board with ICH7R can merge RAID-5 and RAID-0 if they have four of the same drives.
How is this implemented in practice? Let's look at the simpler case of RAID-0 and RAID-1. Let's say you bought two 400 GB hard drives. You partition each drive into 100GB and 300GB logical drives. Then, using the BIOS-based Intel Application Accelerator RAID Option ROM utility, you combine 100GB partitions into a stripe array (RAID-0), and 300GB partitions into a Mirror array (RAID-1). Now, on a fast disk with a volume of 200 GB, you can add, say, toys, video material and other data that require high speed of the disk subsystem and, moreover, are not very important (that is, those that you will not regret very much about losing), and on a mirrored 300 gigabyte disk you move working documents, mail archive, utility software and other vital files. If one disk fails, you lose what was placed on the stripe array, but the data that you placed on the second logical disk is duplicated on the remaining disk.
Combining the RAID-5 and RAID-0 levels implies that part of the capacity of the four disks is dedicated to the fast stripe array, and the other part (let it be 300 GB on each disk) is in the data blocks and parity blocks, that is, you get one a super-fast 400GB drive (4 x 100GB) and one reliable but less fast 900GB array of 4 x 300GB minus 300GB per parity.
As you can see, this technology is extremely promising, and it would be nice if other manufacturers of chipsets and controllers support it. It is very tempting to have arrays of different levels on two disks, fast and reliable.
These are, perhaps, all types of RAID arrays that are used in home systems. However, in life you may come across RAID-2, 3, 4, 6 and 7. So let's see what these levels are.
RAID-2... In an array of this type, disks are divided into two groups - for data and for error correction codes, and if data is stored on n disks, then n-1 disks are needed to store the correction codes. Data is written to the corresponding hard drives in the same way as in RAID-0; they are divided into small blocks according to the number of disks intended for storing information. The remaining disks store error correction codes, according to which, in the event of a hard drive failure, information recovery is possible. The Hamming method has long been used in ECC memory and allows you to correct small one-bit errors on the fly if they suddenly occur, and if two bits are mistakenly transmitted, this will again be detected using parity systems. However, for the sake of this, no one wanted to keep a cumbersome structure of almost double the number of disks, and this type of array did not become widespread.
Array structure RAID-3 is as follows: in an array of n disks, data is divided into 1 byte blocks and spread across n-1 disks, and another disk is used to store parity blocks. In RAID-2, there were n-1 disks for this purpose, but most of the information on these disks was used only for error correction on the fly, and for simple recovery in the event of a disk failure, a smaller amount of it was enough, and one dedicated hard drive was enough.
Level 3 RAID with a separate disk for storing parity information. There is no backup, but the data can be restored.
Accordingly, the differences between RAID-3 and RAID-2 are obvious: the inability to correct errors on the fly and less redundancy. The advantages are as follows: the speed of reading and writing data is high, and very few disks are required to create an array, only three. But an array of this type is good only for single-tasking work with large files, since there are speed problems with frequent requests for small data.
A Level 5 array differs from RAID-3 in that parity blocks are evenly scattered across all disks in the array.
RAID-4similar to RAID-3, but different from it in that the data is broken up into blocks, not bytes. Thus, it was possible to "defeat" the problem of low data transfer rate of small volume. Writing is slow because block parity is generated on write and written to a single disk. Arrays of this type are rarely used.
RAID-6 - this is the same RAID-5, but now two parity blocks are stored on each of the disks in the array. Thus, if two disks fail, the information can still be recovered. Of course, the increased reliability led to a decrease in the usable volume of disks and to an increase in the minimum number of them: now, if there are n disks in the array, the total volume available for data recording will be equal to the volume of one disk multiplied by n-2. The need to calculate two checksums at once determines the second drawback inherited by RAID-6 from RAID-5 - low data write speed.
RAID-7is a registered trademark of Storage Computer Corporation. The structure of the array is as follows: data is stored on n-1 disks, one disk is used to store parity blocks. But several important details have been added to eliminate the main drawback of arrays of this type: data cache and a fast controller that manages the processing of requests. This reduced the number of disk accesses to compute the data checksum. As a result, it was possible to significantly increase the speed of data processing (in some places, five or more times).
RAID 0 + 1 array, or a design of two RAID-1 arrays combined into RAID-0. Reliable, fast, expensive.
New disadvantages have also been added: the very high cost of implementing such an array, the complexity of its maintenance, the need for an uninterruptible power supply to prevent data loss in the cache memory during power outages. You are unlikely to find an array of this type, and if you suddenly see it somewhere, write to us, we will also look at it with pleasure.
Array creation
I hope you have already mastered the choice of the array type. If your board has a RAID controller, you will not need anything other than the required number of disks and drivers for this controller itself. By the way, keep in mind: it makes sense to combine only disks of the same size into arrays, and better than one model. The controller may refuse to work with disks of different sizes, and, most likely, you will be able to use only a part of a large disk equal in volume to the smaller of the disks. In addition, even the speed of the stripe array will be determined by the speed of the slowest disk. And my advice to you is, don't try to make the RAID bootable. It is possible, but in the event of any system failures, you will have a hard time, since recovery will be very difficult. In addition, it is dangerous to place several systems on such an array: almost all programs responsible for selecting an OS kill information from the service areas of the hard drive and, accordingly, spoil the array. It is better to choose a different scheme: one disk is bootable, and the rest are combined into an array.
Matrix RAID in action. Part of the disk space is used by the RAID-0 array, the rest of the space is taken up by the RAID-1 array.
Each RAID array starts with a BIOS RAID controller. Sometimes (only in the case of integrated controllers, and even then not always) it is built into the main BIOS of the motherboard, sometimes it is located separately and is activated after passing a self-test, but in any case, you need it there. It is in the BIOS that the required array parameters are set, as well as the sizes of data blocks, used hard drives, and so on. After you determine all this, it will be enough to save the settings, exit the BIOS and return to the operating system.
There it is necessary to install the controller drivers (as a rule, a floppy disk with them is attached to the motherboard or to the controller itself, but they can be written to a disk with other drivers and service software), reboot, and that's it, the array is ready to go. You can split it into logical drives, format and fill with data. Just remember that RAID is not a panacea. It will save you from data loss in the event of a hard drive crash and minimize the consequences of such an outcome, but it will not save you from power surges and failures of a poor-quality power supply that kills both drives at once, regardless of their "massiveness".
A disdainful attitude to high-quality power supply and temperature conditions of disks can significantly shorten the life of an HDD, sometimes all disks in an array fail, and all data is irretrievably lost. In particular, modern hard drives (especially IBM and Hitachi) are very sensitive to the + 12V channel and do not like even the slightest voltage change on it, so before purchasing all the equipment necessary for building an array, you should check the corresponding voltages and, if necessary, turn on a new one. BP to the shopping list.
Powering hard drives, as well as all other components, from a second power supply unit, at first glance, is easy to implement, but such a power scheme has a lot of pitfalls, and you need to think a hundred times before deciding to take such a step. With cooling, everything is simpler: you just need to provide airflow to all hard drives, plus do not put them close to each other. Simple rules, but, unfortunately, not all follow them. And it is not uncommon for both disks in an array to die at the same time.
In addition, RAID does not replace the need for regular data backups. Mirroring is mirroring, but if you accidentally mess up or erase files, the second disk will not help you in any way. So make a backup whenever you can. This rule applies regardless of the presence of RAID arrays inside the PC.
So, are you RAIDy? Yes? Fine! Just in pursuit of volume and speed, do not forget another proverb: "Make a fool pray to God, he will break his forehead." Strong drives and reliable controllers!
The cost benefit of noisy RAID
RAID is good even without looking at the money. But let's calculate the price of the simplest stripe array of 400 GB. Two Seagate Barracuda SATA 7200.8 drives of 200 GB each will cost you about $ 230. RAID controllers are built into most motherboards, so we get them for free.
At the same time, a 400 GB drive of the same model costs $ 280. The difference is $ 50, and with that money you can get the powerful PSU that you will undoubtedly need. I'm not even talking about the fact that the performance of a composite "disk" at a lower price will be almost twice the performance of a single hard drive.
Let's calculate now, focusing on the total volume of 250 GB. There are no 125 GB drives, so let's take two 120 GB hard drives. The price of each disk is $ 90, the price of one 250 GB hard drive is $ 130. Well, with such volumes, performance comes at a price. And if you take a 300 GB array? Two 160 GB disks - about $ 200, one 300 GB - $ 170 ... Again, not that. It turns out that RAID is beneficial only when using very large disks.
Today we will learn interesting information about what a RAID array is and what role these arrays play in the life of hard drives, yes, in them.
The hard drives themselves play a rather important role in the computer, since with the help of them we start the system and store a lot of information on them.
Time passes and any hard drive can fail, it can be any that we are not talking about today.
I hope that many have heard of the so-called raid arrays, which allow not only to speed up the work of hard drives, but also, if something happens, to save important data from disappearing, perhaps forever.
Also, these arrays have serial numbers, which makes them different. Each has a different function. For example, there is RAID 0, 1, 2, 3, 4, 5 and so on. Today we are going to talk about these very arrays, and then I will write an article on how to use some of them.
What is a RAID array?
RAID Is a technology that allows you to combine several devices, namely, hard drives, in our case something like a bundle of them goes. Thus, we improve data storage reliability and read / write speed. Perhaps one of these functions.
So, if you want to either speed up your disk or just secure your information, it's up to you. More precisely, it depends on the choice of the required configuration of the "Raid", these configurations are marked with serial numbers 1, 2, 3 ...
Raids are a very useful feature and I recommend everyone to use it. For example, if you use 0th configuration, you will feel an increase in the speed of the hard disk, after all, the hard disk is almost the lowest-speed device.
If you ask why, then I think everything is clear. every year they become more powerful, they are equipped with a higher frequency, more cores, and much more. The same with and. And so far, hard drives are growing only in volume, and the turnover rate has remained as it was 7200, and remains. Of course, there are also rarer models. The situation is so far saved by the so-called, which speed up the system several times.
Let's say you went to build RAID 1, in this case, you will receive a high guarantee of the protection of your data, since they will be duplicated on another device (disk) and if one hard disk fails, all the information will remain on the other.
As you can see from the examples, raids are very important and useful and should be used.
So, a RAID array is physically a bundle of two hard disks connected to the motherboard, you can either three or four. By the way, it should also support the creation of RAID arrays. Connecting hard drives is carried out according to the standard, and the creation of raids takes place at the software level.
When we programmatically created the raid, nothing really changed by eye, you just work in the BIOS, and everything else will remain as it was, that is, looking into My Computer, you will see all the same connected disks.
It doesn't take much to create an array: a motherboard with RAID support, two identical hard drives ( it is important). They should be the same not only in volume, but also in cache, interface, etc. It is desirable that the manufacturer is the same. Now we turn on the computer and, there we are looking for the parameter SATA Configuration and put on RAID... After restarting the computer, a window should appear in which we will see information about disks and raids. There we must press CTRL + Ito start configuring the raid, that is, add or remove disks from it. Then its setting will begin.
How many raids are there? There are several of them, namely RAID 1, RAID 2, RAID 3, RAID 4, RAID 5, RAID 6... In more detail, I will talk about only two of them.
- RAID 0 - allows you to create a disk array in order to increase the read / write speed.
- RAID 1 - allows you to create mirrored disk arrays for data protection.
What is RAID 0?
Array RAID 0, also called "Striping" uses 2 to 4 hard drives, rarely more. They work together to increase productivity. Thus, the data with such an array is divided into data blocks, and then written to several disks at once.
Performance is improved by writing one block of data to one disk, to another disk, another block, and so on. I think it is clear that 4 disks will increase performance more than two. If we talk about security, then it suffers on the entire array. If one of the disks fails, then in most cases, all information will be lost forever.
The fact is that in a RAID 0 array, information is located on all disks, that is, the bytes of a file are located on several disks. Therefore, if one disk fails, a certain amount of data will be lost, and recovery is impossible.
It follows from this that it is necessary to make permanent on external media.
What is RAID 1?
Array RAID 1, it is also called Mirroring - mirror. If we talk about the disadvantage, then in RAID 1 the volume of one of the hard disks is, as it were, "unavailable" to you, because it is used to duplicate the first disk. In RAID 0, this space is available.
From the advantages, as you probably already guessed, it follows that the array provides high data reliability, that is, if one disk fails, all data will remain on the second. Failure of two disks at once is unlikely. Such an array is often used on servers, but this does not prevent its use on ordinary computers.
If you choose RAID 1, then know that performance will drop, but if data is important to you, then use the data approach.
What is RAID 2-6?
Now I will briefly describe the rest of the arrays, so to speak, for general development, and all because they are not as popular as the first two.
RAID 2 - needed for arrays that use Hamming code (not interested in what kind of code). The principle of operation is approximately the same as in RAID 0, that is, the information is also divided into blocks and alternately written to disks. The rest of the disks are used to store error correction codes, with the help of which, in the event of a failure of one of the disks, you can restore data.
True, for this array it is better to use 4 disks, which is quite expensive, and as it turned out, when using so many disks, the performance gain is rather controversial.
RAID 3, 4, 5, 6 - I will not write about these arrays here, since the necessary information is already on Wikipedia, if you want to know about these arrays, then we read.
How to choose a RAID array?
Suppose that you often install various programs, games and copy a lot of music or movies, then you are advised to use RAID 0. When choosing hard drives, be careful, they must be very reliable so as not to lose information. Be sure to back up your data.
Is there important information that needs to be safe and sound? Then RAID 1 comes to the rescue. When choosing hard drives, their characteristics must also be identical.
Output
So we have sorted out for someone new, but for someone old information on RAID arrays. I hope this information is useful to you. I will write about how to create these arrays soon.
Good day, dear friends, acquaintances, readers, admirers and other personalities. Today again about the raid array and its creation, configuration, etc.
As you remember, I have repeatedly written about the fact that hard drives are one of the bottlenecks in the performance of your computer. With the advent of SSD, the situation has changed significantly, but not that radically.
If you think about it, then, in general, disks are a "bottleneck" also safe, because: "disk skip \u003d kirdyk data" (unless, of course, they cannot be restored to). RAID arrays are able to solve both of these problems, therefore, in fact, they are used in servers. However, you can successfully use them at home, and you don't need much for this (support for raids with a motherboard + a pair of identical disks).
I already wrote about what RAID is in the article "", but I will tell you about how quickly and easily it is to make RAID at home using regular methods in the text below.
Let's get started.
We create a raid array based on the built-in controller
As I said above, yours must support the creation of RAID "a. The instructions below are relevant for ASUS motherboards based on the UEFI-BIOS, but the general principle is similar as such, therefore, the manual is still recommended for everyone.
First, we go into the BIOS using the appropriate key (usually DEL), and there we find the section responsible for the parameters for the SATA controller (I hope that IDE is no longer used anywhere).
Where do we switch the position of the controller in RAID (usually there is ACHI). Let me remind you that the disks should ideally be identical (preferably absolutely, and not just in size). Further, in fact, we reboot, having previously saved the changes in the BIOS.
At the stage of initializing disks, that is, even before loading the operating system, it will be necessary to press, as a rule (but not always) CTRL-F or CTRL-I. In general, watch carefully, because usually it shows which key combination you need to poke (there are also all kinds of F1-F12).
The simplest menu can be seen in the screenshot above. It does not represent anything complicated and conditionally looks like this:
- View Drive Assignments, - shows drives that are suitable for creating an array;
- LD View / LD Define Menu, - shows the current arrays;
- Delete LD Menu, - allows you to delete arrays;
- Controller Configuration, in fact, is directly responsible for the settings.
We, in the framework of creating such a thing as a raid array, in fact, we are only interested in the second item. By clicking on the corresponding button on the keyboard (i.e. number 2) we get to the corresponding menu.
Here we can see the current arrays (in fact, they are visible in the screenshot), look at their settings (Enter), look at disks outside the RAID (Ctrl + V), or, say, create new raids (Ctrl + C). We are interested in creation, and therefore press the appropriate key combination.
Next, we will observe the menu for creating a RAID (top) and the lonely (outside the arrays) disks themselves (below). Parameters are switched with a space, the parameter items themselves are changed by keyboard arrows.
Let me remind you that the 1st raid is a "mirror", that is, the disks duplicate each other, and even if one fails, then a complete copy of the data remains on the second.
0, on the other hand, is responsible for performance, that is, both disks work in pairs to achieve the maximum available read / write speed. In more detail, I described everything under the link that I gave at the very beginning of the article.
Further steps to create
The screenshot above contains everything needed to create a RAID 1 (mirror), although there was nothing special to set there: all the parameters were left by default, the raid type was selected and two terabyte disks were indicated (Y in the Assingment column). That's all. I do not want to go into details of all the parameters now, because this is a topic for a separate article (briefly from the practical side, on sonikelf.name).
After setting everything you need, press CTRL-Y. Next, either press any button (set the default name), or repeat pressing CTRL-Y to set the name yourself. I chose the second path:
At the next stage, due to the fact that we have selected the standard fast initialization option, a warning will appear stating that data from the disks will be deleted. Press CTRL-Y, if you are sure that there is nothing you need on the disks.
At the last stage, you will be asked to choose the size that will be allocated for the raid array or take up all the available space on the disks. In this paragraph, I chose the solution to take up all the space on the disks (which, by the way, I recommend to you), by pressing any button on the keyboard.
At this, the creation of the RAID can be considered complete, it remains only to exit the wizard and restart the computer.
Oh, and yes, do not forget, if necessary, to go to the Disk Management wizard and initialize and allocate space on the newly created RAID array. The master lives along the way " Control Panel - Administrative Tools - Computer Management - Disk Management".
Well, in fact, the allocation of space, that is, the creation of partitions, also does not cause any problems and is performed in a standard way:
And, yes, it will be useful to install drivers for such a thing as a raid array, unless of course they have been with you for a long time. The drivers are taken from the disk to the motherboard or from the manufacturer's website for this motherboard.
On this sim, perhaps, everything.
Afterword
That's it. Briefly, quickly and clearly (although, I admit that the photos are not the best, but taking screenshots with an emulator or a DSLR is somehow not handy, after all, in this case, the main point is), but now you can quickly assemble a raid array.
As always, if you have any questions, additions, thoughts and all that stuff, then welcome to the comments on this post.
Stay with us;)
