What is raid 1 mirror. What are RAID arrays and why are they needed?
Hello to all site readers! Friends, I have long wanted to talk to you about how to create a RAID array (redundant array of independent disks) on a computer. Despite the apparent complexity of the issue, in fact everything is very simple and I am sure that many readers will immediately adopt and enjoy using this very useful technology related to the security of your data.
How to create RAID array and why it is needed
It's no secret that our information on a computer is practically uninsured and is located on a simple hard drive, which tends to break down at the most inopportune moment. It has long been recognized that the hard drive is the weakest and most unreliable place in our system unit, since it has mechanical parts. Those users who have ever lost important data (myself included) due to the failure of the “screw”, after grieving for some time, are wondering how to avoid such trouble in the future and the first thing that comes to mind is this creating a RAID array.
The whole point of having a redundant array of independent disks is to save your files on your hard drive in the event of a complete failure of that drive! How to do this, you ask, it’s very simple, you only need two (maybe even different in volume) hard drives.
In today's article, using the Windows 8.1 operating system, we will create the simplest and most popular hard drive from two blank hard drives. RAID 1 array, it is also called “Mirroring”. The meaning of a “mirror” is that the information on both disks is duplicated (written in parallel) and the two hard drives are exact copies of each other.
If you copied a file to the first hard drive, then exactly the same file appears on the second and, as you already understood, if one hard drive fails, then all your data will remain intact on second hard drive ( mirror). The probability of failure of two hard drives at once is negligible.
The only disadvantage of a RAID 1 array is that you need to buy two hard drives, but they will work as one single one, that is, if you install two 500 GB hard drives in the system unit, then the same 500 will be available for storing files GB, not 1TB.
If one of the two hard drives fails, you simply take it and replace it, adding it as a mirror to an already installed hard drive with data and that’s it.
Personally, for many years, I use it at work RAID 1 array of two 1 TB hard drives and a year ago something bad happened, one hard drive gave up life, I had to replace it immediately, then I thought with horror what would happen if I didn’t have a RAID array, a slight chill ran through me on the back, because the data accumulated over several years of work would have disappeared, and so, I simply replaced the faulty “terabyte” and continued working. By the way, at home I also have a small RAID array of two 500 GB hard drives.
Software creation RAID 1 an array of two empty hard drives using Windows 8.1
First of all, we install two clean hard drives in our system unit. For example, I will take two 250 GB hard drives.
Open Disk Management
Disk 0- SSD solid state drive with Windows 8.1 operating system installed on partition (C:).
Disc 1 And Disc 2- hard drives with a capacity of 250 GB from which we will assemble a RAID 1 array.
Right-click on any hard drive and select “Create mirror volume”
Add a disk that will be a mirror for the previously selected disk. We selected Disk 1 as the first mirrored volume, which means we select Disk 2 on the left side and click on the “Add” button.
Select the letter of the software RAID 1 array, I leave the letter (D:). Further
Check the Quick Format box and click Next.
In Disk Management, mirrored volumes are indicated by blood red and have a single drive letter, in our case (D:). Copy any files to any disk and they will immediately appear on another disk.
In the This PC window, software RAID 1 array appears as one disk.
If one of the two hard drives fails, then in disk management the RAID array will be marked with the error “Failed Redundancy”, but all data on the second hard drive will be safe.
Greetings to all, dear readers of the blog site. I think many of you have at least once come across such an interesting expression on the Internet - “RAID array”. What it means and why the average user might need it, that’s what we’ll talk about today. It is a well-known fact that it is the slowest component in a PC, and is inferior to the processor and.
To compensate for the “innate” slowness where it is completely out of place (we are talking primarily about servers and high-performance PCs), they came up with the use of a so-called RAID disk array - a kind of “bundle” of several identical hard drives operating in parallel. This solution allows you to significantly increase the speed of operation coupled with reliability.
First of all, a RAID array allows you to provide high fault tolerance for the hard drives (HDD) of your computer by combining several hard drives into one logical element. Accordingly, to implement this technology you will need at least two hard drives. In addition, RAID is simply convenient, because all the information that previously had to be copied to backup sources (external hard drives) can now be left “as is”, because the risk of its complete loss is minimal and tends to zero, but not always, about this a little lower.
RAID translates roughly like this: a protected set of inexpensive disks. The name comes from the times when large hard drives were very expensive and it was cheaper to assemble one common array of smaller disks. The essence has not changed since then, in general, like the name, only now you can make just a gigantic storage out of several large HDDs, or make it so that one disk duplicates another. You can also combine both functions, thereby getting the advantages of one and the other.
All these arrays are under their own numbers, most likely you have heard about them - raid 0, 1...10, that is, arrays of different levels.
Types of RAID
Speed Raid 0
Raid 0 has nothing to do with reliability, because it only increases speed. You need at least 2 hard drives, and in this case the data will be “cut” and written to both disks simultaneously. That is, you will have access to the full capacity of these disks, and theoretically this means that you get 2 times higher read/write speeds.
But let's imagine that one of these disks breaks down - in this case, the loss of ALL your data is inevitable. In other words, you will still have to make regular backups in order to be able to restore the information later. Typically 2 to 4 disks are used here.
Raid 1 or “mirror”
Reliability is not compromised here. You get the disk space and performance of only one hard drive, but you have double the reliability. One disk breaks - the information will be saved on the other.
The RAID 1 level array does not affect the speed, but the volume - here you have at your disposal only half of the total disk space, of which, by the way, in RAID 1 there can be 2, 4, etc., that is, an even number. In general, the main feature of a first-level raid is reliability.
Raid 10
Combines all the best of the previous types. I propose to look at how this works using the example of four HDDs. So, information is written in parallel on two disks, and this data is duplicated on two other disks.
The result is an increase in access speed by 2 times, but also the capacity of only two of the four disks of the array. But if any two disks fail, no data loss will occur.
Raid 5
This type of array is very similar to RAID 1 in its purpose, only now you need at least 3 disks, one of them will store the information necessary for recovery. For example, if such an array contains 6 HDDs, then only 5 of them will be used to record information.
Due to the fact that data is written to several hard drives at once, the reading speed is high, which is perfect for storing a large amount of data there. But, without an expensive raid controller, the speed will not be very high. God forbid one of the disks breaks - restoring information will take a lot of time.
Raid 6
This array can survive the failure of two hard drives at once. This means that to create such an array you will need at least four disks, despite the fact that the write speed will be even lower than that of RAID 5.
Please note that without a powerful raid controller, such an array (6) is unlikely to be assembled. If you only have 4 hard drives, it is better to build RAID 1.
How to create and configure a RAID array
RAID controller
A raid array can be made by connecting several HDDs to a computer motherboard that supports this technology. This means that such a motherboard has an integrated controller, which is usually built into the . But, the controller can also be external, which is connected via a PCI or PCI-E connector. Each controller, as a rule, has its own configuration software.
The raid can be organized both at the hardware level and at the software level; the latter option is the most common among home PCs.
Users do not like the controller built into the motherboard because of its poor reliability. In addition, if the motherboard is damaged, data recovery will be very problematic. At the software level, the role of the controller is played, if something happens, you can easily transfer your raid array to another PC.
Hardware
- How to make a RAID array? To do this you need:
- Get it somewhere with raid support (in the case of hardware RAID);
- Buy at least two identical hard drives. It is better that they are identical not only in characteristics, but also of the same manufacturer and model, and connected to the mat. board using one.
- Transfer all data from your HDDs to other media, otherwise they will be destroyed during the raid creation process.
- Next, you will need to enable RAID support in the BIOS, but I can’t tell you how to do this in the case of your computer, due to the fact that everyone’s BIOS is different. Usually this parameter is called something like this: “SATA Configuration or Configure SATA as RAID”.
Then restart your PC and a table with more detailed raid settings should appear. You may have to press the key combination "ctrl+i" during the POST procedure for this table to appear. For those who have an external controller, you will most likely need to press “F2”. In the table itself, click “Create Massive” and select the required array level.
After creating a raid array in the BIOS, you need to go to “disk management” in OS –10 and format the unallocated area - this is our array.
Program
To create a software RAID, you don't have to enable or disable anything in the BIOS. In fact, you don't even need raid support on your motherboard. As mentioned above, the technology is implemented using the PC’s central processor and Windows itself. Yep, you don't even need to install any third-party software. True, in this way you can only create a RAID of the first type, which is a “mirror”.
In this utility, mirrored volumes are highlighted in one color (red) and are designated by one letter. In this case, the files are copied to both volumes, once to one volume, and the same file is copied to the second volume. It is noteworthy that in the “my computer” window our array will be displayed as one section, the second section is hidden so as not to be an eyesore, because the same duplicate files are located there.
If a hard drive fails, the “Failed Redundancy” error will appear, while everything on the second partition will remain intact.
Let's summarize
RAID 5 is needed for a limited range of tasks, when a much larger number of HDDs (than 4 disks) are assembled into huge arrays. For most users, raid 1 is the best option. For example, if there are four disks with a capacity of 3 terabytes each, in RAID 1 in this case 6 terabytes of capacity are available. RAID 5 in this case will provide more space, however, the access speed will drop significantly. RAID 6 will give the same 6 terabytes, but even lower access speed, and will also require an expensive controller.
Let's add more RAID disks and you will see how everything changes. For example, let’s take eight disks of the same capacity (3 terabytes). In RAID 1, only 12 terabytes of space will be available for recording, half of the volume will be closed! RAID 5 in this example will give 21 terabytes of disk space + it will be possible to get data from any one damaged hard drive. RAID 6 will give 18 terabytes and data can be obtained from any two disks.
In general, RAID is not a cheap thing, but personally I would like to have at my disposal a RAID of the first level of 3 terabyte disks. There are even more sophisticated methods, like RAID 6 0, or “raid from raid arrays”, but this makes sense with a large number of HDDs, at least 8, 16 or 30 - you must agree, this goes far beyond the scope of normal “household” use and is used demand is mostly in servers.
Something like this, leave comments, add the site to bookmarks (for convenience), there will be many more interesting and useful things, and see you soon on the blog pages!
Many users have heard about the concept of RAID disk arrays, but in practice few people imagine what it is. But as it turns out, there is nothing complicated here. Let's look at the essence of this term, as they say, on the fingers, based on the explanation of information for the average person.
What are RAID disk arrays?
First, let's look at the general interpretation offered by online publications. Disk arrays are entire information storage systems consisting of a combination of two or more hard drives that serve either to increase the speed of access to stored information or to duplicate it, for example, when saving backup copies.
In this combination, the number of hard drives in terms of installation theoretically has no restrictions. It all just depends on how many connections the motherboard supports. Actually, why are RAID disk arrays used? Here it is worth paying attention to the fact that in the direction of technology development (relative to hard drives), they have long frozen at one point (spindle speed 7200 rpm, cache size, etc.). The only exceptions in this regard are SSD models, but even they mainly only increase the volume. At the same time, progress in the production of processors or RAM strips is more noticeable. Thus, due to the use of RAID arrays, the performance gain when accessing hard drives is increased.
RAID disk arrays: types, purpose
As for the arrays themselves, they can be conditionally divided according to the numbering used (0, 1, 2, etc.). Each such number corresponds to the performance of one of the declared functions.
The main ones in this classification are disk arrays with numbers 0 and 1 (later it will be clear why), since they are the ones assigned the main tasks.
When creating arrays with multiple hard drives connected, you should initially use the BIOS settings, where the SATA configuration section is set to RAID. It is important to note that the connected drives must have absolutely identical parameters in terms of volume, interface, connection, cache, etc.
RAID 0 (Striping)
Zero disk arrays are essentially designed to speed up access to stored information (writing or reading). As a rule, they can have from two to four hard drives in combination.
But the main problem here is that when you delete information on one of the disks, it disappears on the others. Information is written in the form of blocks alternately on each disk, and the increase in performance is directly proportional to the number of hard drives (that is, four disks are twice as fast as two). But the loss of information is only due to the fact that the blocks can be located on different disks, although the user in the same “Explorer” sees the files in a normal display.
RAID 1
Disk arrays with a single designation belong to the Mirroring category and are used to save data by duplicating.
Roughly speaking, in this state of affairs, the user loses somewhat in productivity, but he can be sure that if data disappears from one partition, it will be saved in another.
RAID 2 and higher
Arrays numbered 2 and higher have dual purpose. On the one hand, they are designed to record information, on the other hand, they are used to correct errors.
In other words, disk arrays of this type combine the capabilities of RAID 0 and RAID 1, but are not particularly popular among computer scientists, although their operation is based on the use
What is better to use in practice?
Of course, if you plan to use resource-intensive programs on your computer, for example, modern games, it is better to use RAID 0 arrays. If you work with important information that needs to be saved in any way, you will have to turn to RAID 1 arrays. Due to the fact that the links with numbers from two and higher never became popular; their use is determined solely by the desire of the user. By the way, the use of zero arrays is also practical if the user often downloads multimedia files to the computer, say, movies or music with a high bitrate for the MP3 format or in the FLAC standard.
For the rest, you will have to rely on your own preferences and needs. The use of this or that array will depend on this. And, of course, when installing a bundle, it is better to give preference to SSD drives, since compared to conventional hard drives they already have higher write and read speeds. But they must be absolutely identical in their characteristics and parameters, otherwise the connected combination simply will not work. And this is precisely one of the most important conditions. So you will have to pay attention to this aspect.
Today we will talk about RAID arrays. Let's figure out what it is, why we need it, what it is like and how to use all this magnificence in practice.
So, in order: what is RAID array or simply RAID? This abbreviation stands for "Redundant Array of Independent Disks" or "redundant (backup) array of independent disks." To put it simply, RAID array this is a collection of physical disks combined into one logical disk.
It usually happens the other way around - one physical disk is installed in the system unit, which we divide into several logical ones. Here the situation is the opposite - several hard drives are first combined into one, and then the operating system is perceived as one. Those. The OS firmly believes that it physically only has one disk.
RAID arrays There are hardware and software.
Hardware RAID arrays are created before loading the OS using special utilities built into RAID controller- something like a BIOS. As a result of creating such RAID array already at the OS installation stage, the distribution kit “sees” one disk.
Software RAID arrays are created by OS tools. Those. During boot, the operating system “understands” that it has several physical disks, and only after the OS starts, through software, the disks are combined into arrays. Naturally, the operating system itself is not located on RAID array, since it is set before it is created.
"Why is all this needed?" - you ask? The answer is: to increase the speed of reading/writing data and/or increase fault tolerance and security.
"How RAID array can increase speed or secure data?" - to answer this question, consider the main types RAID arrays, how they are formed and what it gives as a result.
RAID-0. Also called "Stripe" or "Tape". Two or more hard drives are combined into one by sequential merging and summing up the volumes. Those. if we take two 500GB disks and create them RAID-0, the operating system will perceive this as one terabyte disk. At the same time, the read/write speed of this array will be twice as high as that of one disk, since, for example, if the database is physically located in this way on two disks, one user can read data from one disk, and another user can write to another disk at the same time. Whereas, if the database is located on one disk, the hard disk itself will perform read/write tasks of different users sequentially. RAID-0 will allow reading/writing in parallel. As a consequence, the more disks in the array RAID-0, the faster the array itself works. The dependence is directly proportional - the speed increases N times, where N is the number of disks in the array.
At the array RAID-0 there is only one drawback that outweighs all the advantages of using it - the complete lack of fault tolerance. If one of the physical disks of the array dies, the entire array dies. There's an old joke about this: "What does the '0' in the title mean? RAID-0? - the amount of information restored after the death of the array!"
RAID-1. Also called "Mirror" or "Mirror". Two or more hard drives are combined into one by parallel merging. Those. if we take two 500GB disks and create them RAID-1, the operating system will perceive this as one 500GB disk. In this case, the read/write speed of this array will be the same as that of one disk, since information is read/written to both disks simultaneously. RAID-1 does not provide a gain in speed, but provides greater fault tolerance, since in the event of the death of one of the hard drives, there is always a complete duplicate of information located on the second drive. It must be remembered that fault tolerance is provided only against the death of one of the array disks. If the data was deleted purposefully, it is deleted from all disks of the array simultaneously!
RAID-5. A more secure option for RAID-0. The volume of the array is calculated using the formula (N - 1) * DiskSize RAID-5 from three 500GB disks, we get an array of 1 terabyte. The essence of the array RAID-5 is that several disks are combined into RAID-0, and the last disk stores the so-called “checksum” - service information intended to restore one of the array disks in the event of its death. Array write speed RAID-5 somewhat lower, since time is spent calculating and writing the checksum to a separate disk, but the reading speed is the same as in RAID-0.
If one of the array disks RAID-5 dies, the read/write speed drops sharply, since all operations are accompanied by additional manipulations. Actually RAID-5 turns into RAID-0 and if recovery is not taken care of in a timely manner RAID array there is a significant risk of losing data completely.
With an array RAID-5 You can use the so-called Spare disk, i.e. spare. During stable operation RAID array This disk is idle and not used. However, in the event of a critical situation, recovery RAID array starts automatically - information from the damaged one is restored to the spare disk using checksums located on a separate disk.
RAID-5 is created from at least three disks and saves from single errors. In case of simultaneous occurrence of different errors on different disks RAID-5 doesn't save.
RAID-6- is an improved version of RAID-5. The essence is the same, only for checksums, not one, but two disks are used, and the checksums are calculated using different algorithms, which significantly increases the fault tolerance of everything RAID array generally. RAID-6 assembled from at least four disks. The formula for calculating the volume of an array looks like (N - 2) * DiskSize, where N is the number of disks in the array, and DiskSize is the size of each disk. Those. while creating RAID-6 from five 500GB disks, we get an array of 1.5 terabytes.
Write speed RAID-6 lower than RAID-5 by about 10-15%, which is due to additional time spent on calculating and writing checksums.
RAID-10- also sometimes called RAID 0+1 or RAID 1+0. It is a symbiosis of RAID-0 and RAID-1. The array is built from at least four disks: on the first channel RAID-0, on the second RAID-0 to increase read/write speed, and between them in a RAID-1 mirror to increase fault tolerance. Thus, RAID-10 combines the advantages of the first two options - fast and fault-tolerant.
RAID-50- similarly, RAID-10 is a symbiosis of RAID-0 and RAID-5 - in fact, RAID-5 is built, only its constituent elements are not independent hard drives, but RAID-0 arrays. Thus, RAID-50 gives very good read/write speed and contains the stability and reliability of RAID-5.
RAID-60- the same idea: we actually have RAID-6, assembled from several RAID-0 arrays.
There are also other combined arrays RAID 5+1 And RAID 6+1- they look like RAID-50 And RAID-60 the only difference is that the basic elements of the array are not RAID-0 tapes, but RAID-1 mirrors.
How do you understand combined RAID arrays: RAID-10, RAID-50, RAID-60 and options RAID X+1 are direct descendants of the basic array types RAID-0, RAID-1, RAID-5 And RAID-6 and serve only to increase either read/write speed or increase fault tolerance, while carrying the functionality of basic, parent types RAID arrays.
If we move on to practice and talk about the use of certain RAID arrays in life, the logic is quite simple:
RAID-0 We do not use it in its pure form at all;
RAID-1 We use it where read/write speed is not particularly important, but fault tolerance is important - for example, on RAID-1 It’s good to install operating systems. In this case, no one except the OS accesses the disks, the speed of the hard disks themselves is quite sufficient for operation, fault tolerance is ensured;
RAID-5 We install it where speed and fault tolerance are needed, but there is not enough money to buy more hard drives or there is a need to restore arrays in case of damage without stopping work - spare Spare drives will help us here. Common Application RAID-5- data storage;
RAID-6 used where it is simply scary or there is a real threat of death of several disks in the array at once. In practice it is quite rare, mainly among paranoid people;
RAID-10- used where it is necessary to work quickly and reliably. Also the main direction for use RAID-10 are file servers and database servers.
Again, if we simplify further, we come to the conclusion that where there is no large and voluminous work with files, it is quite enough RAID-1- operating system, AD, TS, mail, proxy, etc. Where serious work with files is required: RAID-5 or RAID-10.
The ideal solution for a database server is a machine with six physical disks, two of which are combined into a mirror RAID-1 and the OS is installed on it, and the remaining four are combined into RAID-10 for fast and reliable data processing.
If, after reading all of the above, you decide to install it on your servers RAID arrays, but don’t know how to do it and where to start - contact us! - we will help you select the necessary equipment, as well as carry out installation work for implementation RAID arrays.
Hard drives play an important role in a computer. They store various user information, launch the OS from them, etc. Hard drives do not last forever and have a certain margin of safety. And each hard drive has its own distinctive characteristics.
Most likely, you have heard at some point that so-called raid arrays can be made from ordinary hard drives. This is necessary in order to improve the performance of drives, as well as ensure the reliability of information storage. In addition, such arrays can have their own numbers (0, 1, 2, 3, 4, etc.). In this article we will tell you about RAID arrays.
RAID is a collection of hard drives or a disk array. As we have already said, such an array ensures reliable data storage and also increases the speed of reading or writing information. There are various RAID array configurations, which are marked with numbers 1, 2, 3, 4, etc. and differ in the functions they perform. By using such arrays with configuration 0 you will get significant performance improvements. A single RAID array guarantees complete safety of your data, since if one of the drives fails, the information will be located on the second hard drive.
In fact, RAID array– this is 2 or n number of hard drives connected to the motherboard, which supports the ability to create raids. Programmatically, you can select the raid configuration, that is, specify how these same disks should work. To do this, you will need to specify the settings in the BIOS.
To install the array, we need a motherboard that supports raid technology, 2 identical (in all respects) hard drives, which we connect to the motherboard. In the BIOS you need to set the parameter SATA Configuration: RAID. When the computer boots, press the key combination CTR-I, and already there we configure RAID. And after that, we install Windows as usual.
It is worth paying attention to the fact that if you create or delete a raid, then all information that is on the drives is deleted. Therefore, you must first make a copy of it.
Let's look at the RAID configurations we've already talked about. There are several of them: RAID 1, RAID 2, RAID 3, RAID 4, RAID 5, RAID 6, etc.
RAID-0 (striping), also known as a zero-level array or “null array”. This level increases the speed of working with disks by an order of magnitude, but does not provide additional fault tolerance. In fact, this configuration is a raid array purely formally, because with this configuration there is no redundancy. Recording in such a bundle occurs in blocks, alternately written to different disks of the array. The main disadvantage here is the unreliability of data storage: if one of the array disks fails, all information is destroyed. Why does this happen? This happens because each file can be written in blocks to several hard drives at once, and if any of them malfunctions, the integrity of the file is violated, and, therefore, it is not possible to restore it. If you value performance and regularly make backups, then this array level can be used on your home PC, which will give a noticeable increase in performance.
RAID-1 (mirroring)– “mirror mode”. You can call this level of RAID arrays the paranoid level: this mode gives almost no increase in system performance, but absolutely protects your data from damage. Even if one of the disks fails, an exact copy of the lost one will be stored on another disk. This mode, like the first, can also be implemented on a home PC for people who value the data on their disks extremely highly. 
When constructing these arrays, an information recovery algorithm is used using Hamming codes (an American engineer who developed this algorithm in 1950 to correct errors in the operation of electromechanical computers). To ensure the operation of this RAID controller, two groups of disks are created - one for storing data, the second group for storing error correction codes. 
This type of RAID has become less widespread in home systems due to the excessive redundancy of the number of hard drives - for example, in an array of seven hard drives, only four will be allocated for data. As the number of disks increases, redundancy decreases, which is reflected in the table below.
The main advantage of RAID 2 is the ability to correct errors on the fly without reducing the speed of data exchange between the disk array and the central processor.
RAID 3 and RAID 4
These two types of disk arrays are very similar in design. Both use multiple hard drives to store information, one of which is used exclusively for storing checksums. Three hard drives are enough to create RAID 3 and RAID 4. Unlike RAID 2, data recovery on the fly is not possible - information is restored after replacing a failed hard drive over a period of time.
The difference between RAID 3 and RAID 4 is the level of data partitioning. In RAID 3, information is broken down into individual bytes, which leads to serious slowdown when writing/reading a large number of small files. RAID 4 splits data into separate blocks, the size of which does not exceed the size of one sector on the disk. As a result, the processing speed of small files increases, which is critical for personal computers. For this reason, RAID 4 has become more widespread.
A significant disadvantage of the arrays under consideration is the increased load on the hard drive intended for storing checksums, which significantly reduces its resource.
RAID-5. The so-called fault-tolerant array of independent disks with distributed storage of checksums. This means that on an array of n disks, n-1 disk will be allocated for direct data storage, and the last one will store the checksum of the n-1 stripe iteration. To explain more clearly, let's imagine that we need to write a file. It will be divided into portions of the same length and will alternately begin to be written cyclically to all n-1 disks. A checksum of bytes of data portions of each iteration will be written to the last disk, where the checksum will be implemented by a bitwise XOR operation.
It’s worth warning right away that if any of the disks fail, it will all go into emergency mode, which will significantly reduce performance, because To put the file together, unnecessary manipulations will be performed to restore its “missing” parts. If two or more disks fail at the same time, the information stored on them cannot be restored. In general, the implementation of a level 5 raid array provides fairly high access speeds, parallel access to various files, and good fault tolerance.
To a large extent, the above problem is solved by constructing arrays using the RAID 6 scheme. In these structures, a memory volume equal to the volume of two hard drives is allocated for storing checksums, which are also cyclically and evenly distributed to different disks. Instead of one, two checksums are calculated, which guarantees data integrity in the event of simultaneous failure of two hard drives in the array.
The advantages of RAID 6 are a high degree of information security and less performance loss than in RAID 5 during data recovery when replacing a damaged disk.
The disadvantage of RAID 6 is that the overall data exchange speed is reduced by approximately 10% due to an increase in the volume of necessary checksum calculations, as well as due to an increase in the amount of information written/read.
Combined RAID types
In addition to the main types discussed above, various combinations of them are widely used, which compensate for certain disadvantages of simple RAID. In particular, the use of RAID 10 and RAID 0+1 schemes is widespread. In the first case, a pair of mirrored arrays are combined into RAID 0, in the second, on the contrary, two RAID 0 are combined into a mirror. In both cases, the increased performance of RAID 0 is added to the information security of RAID 1.
Often, in order to increase the level of protection of important information, RAID 51 or RAID 61 construction schemes are used - mirroring of already highly protected arrays ensures exceptional data safety in the event of any failures. However, it is impractical to implement such arrays at home due to excessive redundancy.
Building a disk array - from theory to practice
A specialized RAID controller is responsible for building and managing the operation of any RAID. To the great relief of the average personal computer user, in most modern motherboards these controllers are already implemented at the chipset southbridge level. So, to build an array of hard drives, all you have to do is purchase the required number of them and determine the desired RAID type in the appropriate section of the BIOS settings. After this, instead of several hard drives in the system, you will see only one, which can be divided into partitions and logical drives if desired. Please note that those who are still using Windows XP will need to install an additional driver.
And finally, one more piece of advice - to create a RAID, purchase hard drives of the same capacity, the same manufacturer, the same model, and preferably from the same batch. Then they will be equipped with the same logic sets and the operation of the array of these hard drives will be the most stable.
Tags: , https://site/wp-content/uploads/2017/01/RAID1-400x333.jpg 333 400 Leonid Borislavsky /wp-content/uploads/2018/05/logo.pngLeonid Borislavsky 2017-01-16 08:57:09 2017-01-16 07:12:59 What are RAID arrays and why are they needed?
