What does it all mean, when do I use what?
What Is RAID?
RAID stands for redundant array of inexpensive disks; or now more commonly redundant array of independent disks.
The idea of RAID is to use multiple disk in conjunction with each other to create 1 logical Volume. For example, you would use RAID to couple together 4x1TB hard drives to create what looks like 1 4TB hard drive. Each RAID configuration has it's own purpose and will be used for completely different applications.
For instance, RAID 1 would be used for backup purposes and redundancy while RAID 5 would be used to create larger logical volumes out of many smaller hard drives.
Have a look at the table below. It breaks down each configuration by it's name and description.
|Level||Description||Minimum Drives||Fault tolerance||Read perf.||Write perf.|
|RAID 0||Block-level striping without parity or mirroring||2||0 (none)||n×||n×|
|RAID 1||Mirroring without parity or striping||2||n−1 drives||n×||1×|
|RAID 2||Bit-level striping with dedicated Hamming-code parity||3||One drive||(Varies)||(Varies)|
|RAID 3||Byte-level striping with dedicated parity||3||One drive||(n−1)||(n−1)|
|RAID 4||Block-level striping with dedicated parity||3||One drive||(n−1)||(n−1)|
|RAID 5||Block-level striping with distributed parity||3||One drive||n||(n−1)|
|RAID 6||Block-level striping with double distributed parity||4||Two drives||n||(n−2)|
|RAID 1+0||Mirroring without parity, and block-level striping||4||One or more drives per span||(n/spans)|