Docu review done: Mon 20 Feb 2023 10:59:23 CET

Raid

Table of content

Raid Levels

RAID LevelRAID 0RAID 1RAID 4RAID 5RAID 6RAID 10
min HDDs223344
functionalityRAID0RAID1RAID4RAID5RAID6RAID10
data safetynoneone dead driveone dead driveone dead drivetwo dead drivesone dead drive per sub-array
kapazity100%50%67% - 94% (by 16 drives)67% - 94% (by 16 drives)50% - 88% (by 16 drives)50%
rebuild after one drive brokenot possiblecopy mirrored driverebuild of content with XOR (all drives need to be fully read)rebuild of content with XOR (all drives need to be fully read)rebuild of content from initial drive (depending on raid 6 level implementation)copy mirrored drive
rebuild after two drives brokenot possiblenot possiblenot possiblenot possiblesame as aboveonly possible if two drives from differnt raids are effected

RAID 0

  • High performance: for reading and writing multible discs can be used
  • No data savety: if one disk breaks the full data is getting lost

RAID0

RAID 1

  • Performance: for writing operations the spead is nearly the same as if you would write to a single disk and for reading it is possible to read from both which means that the read operation can be improved
  • Data savety: the full data is mirrord between the disks/partitions, means one disk/partition can break an no data will be lost

RAID1

RAID 4

RAID 4 is nearly the same as a RAID 5, besides that the parity data is saved on a dedecated disk/partition and not like in RAID 5 splited over disks/partitions

RAID4

RAID 5

  • No data loss on one broken drive/parition
  • Parity data: instead of a full data mirror, the RAID 5 calculates the parity data by using a XOR operations
  • Destination of parity data: the parity data will be splited around each disk/partition
  • High read performance: for huge datastreams the system can get the data from multible disks/partitions
  • Write performance: befor the writing operation, a read operations needs to happen for calculating where the new parity data for the stripe needs to be placed.
  • Repairing broken disk/parition: If a disk/parition in an RAID 5 fails, the data will be calculated (XOR) and reads all available disks/partitions content for restoring

RAID5

RAID 6

  • Corruption of two disks will cause data loss
  • Different RAID 6 implementations: there are several different mathematical posibilities for creating and mantaining duplicate parity data (e.g. Galois field or RAID DP)

RAID6

RAID 10

High performance same as RAID 0 combined with data savety from RAID 1.

RAID10