This document summarizes different RAID levels: RAID 0 uses striping to improve performance but provides no redundancy. RAID 1 uses mirroring to provide redundancy but no performance benefits from striping. RAID 5 uses distributed parity to provide both performance from striping and redundancy, making it a good option for read-heavy databases. RAID 6 adds a second parity block to allow two disk failures but is more complex to implement. RAID 10 uses mirroring and striping to provide both high performance and redundancy, making it best for critical applications. RAID 0+1 mirrors stripes for data replication and sharing across disks.

1. RAID LEVELS
BY
SRIPATI MAHAPATRA

2. RAID 0 (STRIPING)
o Minimum 2 disks.
o Excellent performance ( as blocks are striped ).
o No redundancy ( no mirror, no parity ).
o Don’t use this for any critical system.

3. RAID 1 (MIRRORING)
o Minimum 2 disks.
o Good performance ( no striping. no parity ).
o Excellent redundancy ( as blocks are mirrored ).

4. RAID 5 DISTRIBUTED PARITY
o Minimum 3 disks.
o Good performance ( as blocks are striped ).
o Good redundancy ( distributed parity ).
o Best cost effective option providing both performance and redundancy. Use
this for DB that is heavily read oriented. Write operations will be slow.

5. RAID 6 (BLOCK STRIPING)
o Just like RAID 5, this does block level striping. However, it uses dual parity.
o In the below diagram A, B, C are blocks. p1, p2, p3 are parities.
o This creates two parity blocks for each data block.
o Can handle two disk failure
o This RAID configuration is complex to implement in a RAID controller, as it
has to calculate two parity data for each data block

6. RAID 10 (MIRRORING AND STRIPING)
o Minimum 4 disks.
o This is also called as “stripe of mirrors”
o Excellent redundancy ( as blocks are mirrored )
o Excellent performance ( as blocks are striped )
o If you can afford the dollar, this is the BEST option for any mission critical
applications (especially databases).

7. RAID 0+1
A RAID 0+1 (also called RAID 01), is a RAID level used for both replicating and
sharing data among disks. RAID 0+1 is a mirror of stripes. The usable capacity
of a RAID 0+1 array is the same as a RAID 1 array, where half of the total
capacity is used to mirror the other half.