Raid 4 and RAID 5

Raid 4:

At least three hard disks are required and a disk is designed to store verification codes. However, when data is requested to be written, data is first written to other disks, when the disk is verified, the verification code is calculated and then written to the disk. Then, the verification code is repeatedly written to other disks, and the verification code is repeatedly written to the disk, if the disk1 data disk is damaged and does not affect the system operation, you can calculate the data of disk2 based on the verification code of Disk 2 and verification disk, but it will affect the system operation performance, as shown below:

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Conclusion: at least 3 Fast disks are required.

The read/write performance is the sum of the total number minus the sum of one disk, that is, (n-1)/n, but the write performance is not as good as the read performance, because the write verification code needs to be calculated.

Data security is provided, but data is not absolutely secure. Only one disk can be broken. When there are many data disks, the disk must be frequently accessed. Therefore, the redundancy capability is limited, the disk is heavily dependent on the verification disk.

RAID 5:

The optimization is based on raid 4. The verification is not stored on one disk, but distributed on each hard disk. In this way, the performance is maintained, it also solves the bottleneck of disk Verification:

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Summary RAID5:

Requires at least 3 Fast Disks

The read/write performance is the sum of the total number minus the sum of one disk, that is, (n-1)/n, but the write performance is not as good as the read performance, because the write verification code needs to be calculated.

Data security is provided, but only one disk can be broken. The bottleneck is no longer the data verification disk, because the data verification is stored on average on each disk.

This article is from the "Linux" blog, please be sure to keep this source http://zhangshijie.blog.51cto.com/806066/1572706

Raid 4 and RAID 5