Question

You are implementing a RAID storage system and have found a system with eight 100 GB drives. How much storage space will you have available? How does the OS handle this RAID?

Answer 1

Answer:

The space available will vary between 800 GB (100%) and 400 GB (50%) of the total disks, depending on the RAID level.

The OS will handle the RAID as a single disk.

Explanation:

Each RAID level implements parity and redundancy in a different way, so the amount of disks used for this extra information will reduce the space available for actual storage.

Usual RAID levels are:

RAID 0: does not implement any redundancy or parity, so you will have available 100% of the total storage: 8 x 100 GB = 800 GB

RAID 1: Duplicates all the information in one disk to a second disk. Space is reduced in half: 400 GB

RAID 5: Uses the equivalent of 1 disk of parity data distributed evenly on each disk, meaning the space available is $\frac{n-1}{n}$ of the total disks: $\frac{7}{8}$ of 800 GB = 700 GB

Writting and reading the information on a RAID storage is handled by a raid controller, either implemented in hardware or software. The OS will "see" a single disk and will read or write information as usual.