Summary of Raid0, Raid1, Raid5, and Raid10, raid5raid10

Summary of Raid0, Raid1, Raid5, and Raid10, raid5raid10

RAID0

Definition:

RAID 0, also known as Stripe or Striping, represents the highest storage performance in all RAID levels. RAID 0 improves storage performance by distributing continuous data to multiple disks for access. In this way, the system can execute data requests on multiple disks in parallel, each disk executes its own data request. This type of parallel operations on data can make full use of the bandwidth of the bus, significantly improving the overall disk access performance.

Working principle:

The I/O data requests sent by the system to a three-disk logical hard disk (RAID0 disk group) are converted into three operations, each of which corresponds to one physical hard disk. By creating RAID 0, data requests in the original sequence are distributed to all three hard disks for simultaneous execution. Theoretically, parallel operations on three hard disks increase the disk read/write speed by three times in the same time. However, due to bus bandwidth and other factors, the actual increase rate will certainly be lower than the theoretical value.

Advantages and disadvantages:

Read/write performance is the highest among all RAID levels.

RAID 0 does not provide data redundancy. Therefore, damaged data cannot be recovered once the user data is damaged. When RAID0 is running, if any of the hard disks fails, the entire data may fail. Enterprise Users are generally not recommended to use it independently.

Summary:

Disk space usage: 100%, hence the lowest cost.

Read performance: N * read performance of a single disk

Write Performance: N * Write Performance of a single disk

Redundancy: None. Data is unavailable if any disk is damaged.

 

RAID1

Definition:

RAID 1 achieves data redundancy through disk data mirroring, and generates mutually backed up data on pairs of Independent Disks. When raw data is busy, data can be directly copied from the image, so RAID 1 can improve read performance. RAID 1 is the most costly disk array, but provides high data security and availability. When a disk fails, the system can automatically switch to the image disk to read and write data without restructuring the invalid data.

Working principle:

RAID1 is a RAID disk array composed of two hard disks. Its capacity is equal to the capacity of one hard disk, because the other disk is only used as a data "image ". RAID1 is clearly the most reliable disk array, because it always maintains a complete data backup. Its performance is naturally not as good as the RAID 0 disk array, but its Data Reading speed is indeed faster than that of a single hard disk, because the data will be read from the two hard disks quickly. The write speed of the RAID1 disk array is usually slow, because data must be written to two hard disks and compared. RAID1 disk arrays generally support "Hot Swap", that is, the removal or replacement of hard disks in the array can be performed during system operation without interrupting the system. RAID1 disk array is very secure, but it is also a more expensive RAID disk array solution, because the two hard disks can only provide the capacity of one hard disk. RAID1 disk array is mainly used in scenarios where data security is high and damaged data needs to be quickly restored.

Here, it should be noted that the read can only be performed on one disk and will not be read in parallel. The performance depends on the fast one in the hard disk. Writing is usually slower than writing a single disk. Although writing data to two disks is performed concurrently, the data on the two disks must be compared, therefore, the performance is slower than that of a single disk.

Advantages and disadvantages:

RAID1 achieves data redundancy through hard disk data images to ensure data security. The two disks generate mutually backed up data. When the raw data is busy, you can directly read the data from the image backup, therefore, RAID1 can provide read performance.
RAID1 is the highest unit cost in hard disks, but provides high data security and availability. When a hard disk fails, the system can automatically switch to the image hard disk for read/write, and no invalid data needs to be reorganized.

Summary:

Disk space usage: 50%, so the highest cost.

Read performance: Only one disk can be read, depending on the disk that is faster

Write Performance: Both disks need to be written. Although the data is written in parallel, the performance of a single disk is slow due to comparison.

Redundancy: As long as a disk is available on any one of the system's image disks, the system can run normally even when half of the hard disks are faulty.

 

RAID 5

 

Definition:

RAID 5 is a compromise between RAID 0 and RAID 1. RAID 5 has a Data Reading Speed similar to RAID0, but has an additional parity information. The data writing speed is slightly slower than that of a single disk. At the same time, because multiple pieces of data correspond to one parity information, the disk space utilization of RAID 5 is higher than RAID 1, and the storage cost is relatively low. It is a widely used solution.

Working principle:

RAID5 stores the data and the corresponding parity information on each disk that makes up RAID5, And the parity information and the corresponding data are stored on different disks respectively, any of these N-1 block disks Store complete data, that is, there is space equivalent to a disk capacity for storing parity information. Therefore, when a disk in RAID 5 is damaged, data integrity is not affected, thus ensuring data security. After a damaged disk is replaced, RAID will automatically use the remaining parity information to reconstruct the data on the disk to maintain the high reliability of RAID 5.

The disk capacity of all raid 5 arrays must be the same. When the disk capacity is not the same, the minimum disk capacity will prevail. It is recommended that the disk speed be the same. Otherwise, the performance will be affected, and the available space is equal to the number of disks n-1. Raid 5 does not have an independent parity disk, and all verification information is distributed across all disks, it only occupies the capacity of one disk.

Summary:

Disk Space Utilization (N-1)/N, that is, only one disk is wasted for parity.

Read performance: (n-1) * The read performance of a single disk is close to that of RAID 0.

Write Performance: The Write Performance is worse than that of a single disk (this is not clear, can it be written in parallel ?)

Redundancy: Only one disk is allowed to be damaged.

 

RAID10

Definition:

RAID10 is also called an image array strip. Like RAID0, data is extracted across disks. Like RAID1, each disk has a mirror disk. Therefore, RAID 10 is also called RAID 0 + 1. RAID10 provides 100% data redundancy and supports larger volume sizes, but the price is relatively high. RAID10 provides the best performance for most applications that only require redundancy and do not have to consider the price. RAID10 provides better reliability because data can still be protected even if two physical drives fail (one in each array. RAID10 requires 4 + 2 * N disk drives (N> = 0), and only half of them can be used (or smaller, if the disk size is different, for example, four 250 GB hard disks use the raid 10 array, and the actual capacity is 500 GB.

Implementation principle:

In fact, the structure of Raid10 is very simple. First, create two independent Raid 1, and then combine the two independent Raid 1 into a Raid 0. When writing data to this logical Raid, data is written in two RAID 1 orders. Disk 1 and Disk 2 form a RAID 1, and Disk 3 and disk 4 form another raid 1. These two RAID 1 form a new RAID 0. For example, data 1, 3, 5, and 7 written on Hard Disk 1 is data 1, 3, 5, and 7 written on Hard Disk 2, the data in the hard disk is 0, 2, 4, 6, and the data in hard disk 4 is 0, 2, 4, and 6. Therefore, the data is grouped into RAID 10 on these four hard disks, it has the features of RAID 0 and RAID 1.
Although the Raid10 solution causes 50% of disk waste, it provides 200% speed and data security for a single disk damage, and when the damaged disk is not in the same Raid1, to ensure data security. If a disk in the disk is broken, the entire Logical Disk can still work normally.
When we need to recover the damaged disk in raid 10, we only need to replace the New hard disk and recover the data according to the working principle of RAID 10. During the data recovery process, the system can still work normally. The original data will be synchronized and restored to the replaced hard disk.

Summary:

Disk Space Utilization: 50%.

Read performance: N/2 * read performance of a single hard disk

Write Performance: N/2 * Write Performance of a single hard disk

Redundancy: as long as one disk in an image disk can be used, no problem occurs.

 

Refer:

Baidu encyclopedia

Http://blog.chinaunix.net/uid-639516-id-2692517.html

Http://www.h3c.com.cn/Solution/Multimedia_Communicate/Video_Surveillance_Storage/What_Do_ I _Need/Bookmark/200909/646074_30004_0.htm