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RAID

RAID


  • Stands for Redundant Array of Inexpensive Disks (or Redundant array of Independent Disks)
  • It is a data storage virtualization technology that combines multiple physical disk drives into logical units to ensure data redundancy and performance improvement
  • The standard RAID levels including there features and the number of disks that ensure their functionality are :
RAID levelsFeaturesNumber of disks
RAID 0StripingAt least 2
RAID 1MirroringAt least 2
RAID 5Striping with parityAt least 3 but upto 16
RAID 6Striping with double parityAt least 4
RAID 10Combining mirroring and stripingAt least 4
RAID types

A bit more...


RAID 0 : It improves the disk subsystem performance, but it does not provide fault tolerance

RAID 1: It uses same disks which both hold the same data. If one disk fails, the other disk continues to operate as usual.

RAID 5: It uses three or more disks with the equivalent of one disk holding parity information. If one disk fails, the RAID array will continue to operate. Of course, as you guessed it the performance will take a hit (slowness etc.)

RAID 6: It is same as RAID 5, except that the parity data is written to two drives (hence, at least one more drive compared to RAID 5).. resulting in added redundancy.

RAID 10: You will find this alternatively mentioned as RAID 1 + 0 in various technical documentations. It requires at least four disks but can support more as long as the total number is even. It will continue to operate even if multiple disks fail, as long as at least one drive in each mirror continues to function.

RAID Levels 2, 3, 4 and 7 - What's wrong with them?


                                                                RAID 2, 3, 4 and 7

Well they do exist.. but are not so common in most deployments.


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