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

RAID 5 has to be fault-tolerant and read in parallel, which means one less drive letter capacity (used for fault-tolerant backup). In other words, RAID 0 reduces the drive letter capacity by half.

I was too lazy to play by myself, and copy came over:

The number of disks available for RAID5 is: nMub 1.

That is to say, the usable capacity of the system after RAID5 is: the capacity of a single disk * (nmur1)

So the available capacity of your 4-disk RAID5 is 500G * (4-1) = 1500G=1.5T.

RAID5 stores the data and the corresponding parity information on each disk that makes up the RAID5, and the parity information and the corresponding data are stored on different disks, in which any Nmuri disk stores complete data, that is to say, there is a space equivalent to the capacity of a disk to store parity information. Therefore, when a disk of RAID5 is damaged, it will not affect the integrity of the data, thus ensuring the security of the data. When the 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 RAID5.

RAID5 has nothing to do with hot spares. Hot spares are available or not. It's a little more reliable if you use it. It doesn't matter if you don't need it. It mainly depends on the importance of your data.

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