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RAID

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General Computing

Knowledgebase Article:
RAID = Redundant Array of Inexpensive Disks
RAID 0:
Performance: Best
Fault Tolerance: None
Cost: Cheapest
I/Os per write: 1
RAID 1:
Performance: Good
Fault Tolerance: Yes
Cost: Expensive: 2
I/Os per write: 2
RAID 5:
Performance: Fast reads, slow on writes, due to parity info
Fault Tolerance: Yes, system performance will degrade
Cost: Economical
I/Os per write: 4
RAID 10:
Performance: Good, better than RAID 1
Fault Tolerance: Yes
Cost: Expensive
I/Os per write: 2
Descriptions...
RAID 0
This level is also known as DISK STRIPING because of its use of a disk file system called a stripe set. RAID 0 improves read/write performance by spreading operations across multiple disks, so that operations can be performaed independently and simultaneously. RAID 0 does not provide for fault tolerance. RAID 0 is similar to RAID 5 except for the fault tolerance.
RAID 1
This level is also known as DISK MIRRORING because of its use of a system called a mirror set. Disk mirroring provides a redundant, identical copy of a selected disk. All data written to the primary disk is written to the mirror disk. RAID 1 provides fault tolerance.
RAID 5
Also known as STRIPING WITH PARITY, this level is the most popular strategy for new designs. Data redundancy is provided by the parity information. The data and parity information are arranged on the disk array so that the two are always on different disks. RAID 5 has better read performance than disk mirroring (RAID 1), but write performance is lesser. RAID 5 requires a minimum of 3 disks. When one drive fails, read performance will degrade.
RAID 10 (1 + 0)
This level is also known as MIRRORING WITH STRIPING. This level uses a striped array of disks, which are then mirrored to another identical set of striped disks. For example, a striped array can be created using four disks. The striped array of disks is then mirrored, using another set of four striped disks. RAID 10 provides the performance benfits of disk striping with the disk redundancy of mirroring. RAID 10 provides the highest read/write performance of any RAID level, at the expense of using twice as many disks.

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