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What are the different RAID
levels and what do they support?
Level 0: Disk Striping
- data is transferred in parallel across an array of
disks. Redundancy is not provided in this level.
Level 1: Disk Mirroring
- duplicate contents of one disk are written onto another
disk.
Level 0+1: Disk Striping
and Mirroring - this level combined the performance
of striping with the reliability of of mirroring. This
results in very high I/O performance and high data availability.
Level 2: Bit interleaving
data across multiple disks with parity information created
using a Hamming code. A Hamming code detects errors
that occur and determine which part is in error. RAID
level 2 specifies 39 disks with 32 disks of user storage
and 7 disks of error recovery coding.
Level 3: Data is
striped across multiple drives and parity is written
to a dedicated drive. Level 3 is typically implemented
at the BYTE level.
Level 4: Data is
striped across multiple drives and parity is written
to a dedicated drive. Level 4 is typically implemented
at the BLOCK level.
Level 5: Error correction
data is striped at the block level across all the drives
in the array. Reads and writes may be performed concurrently.
JBOD: "Just a Bunch
Of Drives" - performance without data redundancy.
Use where loss of data is not critical. |
