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RAID definition

RAID (Redundant Array of Independent Disk Independent redundant disk Array) technology was put forward by the University of California, Berkeley in 1987. At first, it developed a certain level of data protection technology in order to combine small cheap disks to replace large expensive disks, and hope that the access to data will not be lost when the disk fails. RAID is a redundant array composed of multiple cheap disks, which appears as an independent large storage device under the operating system. RAID can give full play to the advantages of multiple hard drives, can improve hard disk speed, increase capacity, provide fault tolerance to ensure data security, easy to manage the advantages of any hard disk problems can continue to work, will not be affected by damage to the hard disk.

There are many categories of RAID, but I will only talk about four commonly used RAID (RAID 0 RAID 1 RAID 5 RAID 10)

RAID 0 (also known as Stripe or Striping-- striping)

That is, Data Stripping data striping technology. RAID 0 can connect multiple hard drives into a larger hard disk cluster, which can improve disk performance and throughput. RAID 0 has no redundancy or bug repair capabilities, has a low cost, requires at least two disks, and is generally used only in cases where logarithmic security is not required.

RAID 0 performance and security:

Performance: high read and write performance, high random write performance

Security: no redundancy, no hot spare, no fault tolerance, low security

Graphical representation:

RAID 1 (also known as Mirror or Mirroring-- mirror)

RAID 1 is called disk mirroring: mirroring the data from one disk to another can maximize the reliability and repairable performance of the system, but has a high data redundancy, but the disk utilization is 50%, so the cost is the highest, and it is often used to save critical and important data. RAID 1 operates by automatically copying 100% of the data that the user writes to the hard disk to another hard disk.

RAID 1 performance and security:

Performance: low read and write performance, low random write performance

Security: redundancy with replication, hot spare, fault tolerance and high security

RAID 1 graphical representation:

RAID 5

Distribution of odd and even position bands. It is a storage scheme that takes into account storage performance, data security and storage cost, and can also be understood as a compromise between RAID 0 and RAID 1. The principle is that the data and the corresponding parity information are stored on each disk that makes up the RAID5, and the parity information and the corresponding data are stored on different disks respectively. When a disk data of RAID5 is damaged, the remaining data and corresponding parity information are used to recover the damaged data. Compared to RAID 0, there is only one more parity information. A plurality of data can correspond to a parity information.

RAID 5 performance and security:

Performance: low random and continuous write performance, high read performance

Security: redundancy using parity, fault tolerance and high security

RAID 5 graphical representation:

RAID10

RAID 10 (RAID 1: 0 mirrors first (RAID 1), then stripes (RAID 0))

RAID 01 (RAID 01stripe (RAID 0), then mirror (RAID 1))

Mirror the array stripe. Taking into account both storage performance and data security, it provides the same data security as RAID 1, and has a storage performance similar to RAID 0. The disadvantage is the high cost of storage.

Differences in security between RAID 10 and RAID 01:

1. The situation of RAID10

In this case, we assume that when the DISK0 is damaged, in the remaining 3 disks, only when one of the DISK1 disks fails will it cause the whole RAID to fail. We can simply calculate the failure rate as 1 RAID 3. (two sets of hard drives can break one hard disk at the same time, or only one hard disk in each group, but not both hard drives in the same group.)

2. The situation of RAID01

In this case, we still assume that the DISK0 is corrupted and the left stripe will not be readable. In the remaining 3 disks, as long as either of the two DISK2,DISK3 disks is damaged, it will lead to the failure of the whole RAID, and we can simply calculate the failure rate of 2 prime 3. (two hard drives of the same group can be damaged at the same time, but one hard disk of each group cannot be damaged at the same time)

From the logical location of data storage, under normal circumstances, RAID01 and RAID10 are exactly the same, and the number of IO generated by each read and write operation is the same, so there is no difference in read and write performance. When there is a disk failure, such as the hypothetical DISK0 damage, we can also find that in these two cases, the read performance will also be different, and the read performance of RAID10 will be better than that of RAID01.

RAID 10 and RAID 01 are graphically represented:

Thank you for reading! This is the end of this article on "sample Analysis of disk Array RAID". I hope the above content can be of some help to you, so that you can learn more knowledge. if you think the article is good, you can share it for more people to see!

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