Shulou(Shulou.com)06/01 Report--

RAID (Redundant Array of Independent Disks, redundant Array of Independent disks) can provide higher speed and security of normal side disks. All servers choose to create a RAID when they are installed. There are two ways to create RAID: soft RAID (implemented by operating system software) and hard RAID (using hardware array cards)

1.RAID-0:strinping (stripe mode) requires at least two fast disks, preferably the same size in RAID partitions (can give full play to the advantage of concurrency); data is scattered on different disks and can achieve concurrency when reading and writing, all of which have the best relative read-write performance; but without fault tolerance, damage to any disk will damage all data; disk utilization is 100%

2.RAID-1:mirroring (mirror volume) requires at least two hard disks. The raid size is equal to the minimum capacity of the two raid partitions (it is best to divide the partition size into the same). The data is redundant and is written to two hard disks at the same time to achieve data backup. The disk utilization is 50%, that is, 2 fast 100g hard disks constitute RAID1 that can only provide 100g of available space.

3.RAID-5: three or more hard drives are required, and hot spares can be provided for fault recovery. Only one disk is damaged and there is no problem. However, if both disks are damaged at the same time, the data will be corrupted. Utilization: (nmur1) / n 2max 3

Is a relatively simple XOR logic operation (the same is 0, the difference is 1)

A value B value Xor result

0 0 0

1 0 1

0 1 1

1 1 0

=

The values of An and B here represent two bits, from which it can be found that when An is the same as B, the XOR result is 0 and the XOR result is 1, and if you know the XOR result and any one of An and B, you can send out another value.

Note: hot spare (hot spare or hot standby driver): in order to enhance fault tolerance and enable the system to quickly rebuild data in the event of disk failure, in order to maintain the performance of the system, the general disk array can use the hot backup function.

Chunk (fast): the size of each segment when raid stores data. 4K 64K

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