RAID LEVELS
What is RAID?
➢ Redundant Array of Inexpensive Disks.
Basic idea is to connect multiple disks together to provide
➢ Large storage capacity
➢ Faster access to reading data
➢ Redundant data
Why RAID?
➢ RAID system provides data redundancy, fault tolerance,
increased capacity and increased performance.
➢ RAID has for a long time been something that you only find in
large server systems, but lately cheaper
➢ RAID controller card have made it possible to get a RAID system
even for small servers and home computers.
RAID LEVELS:
➢ RAID 0 – striping
➢ RAID 1 – mirroring
➢ RAID 2 – redundancy through Hamming
➢ RAID 3 – bit interleaved Parity
➢ RAID 4 – block interleaved Parity
➢ RAID 5 – striping with parity
LEVEL 0 (striping):
➢ Striping means that each file is split into blocks of a certain
size and those are distributed to the various drives.
➢ Offers superior I/O performance.
➢ Performance can be enhanced further by using multiple
controllers.
LEVEL 1 (mirroring):
➢ Mirroring means duplication of data i.e
➢ Data are stored twice.
➢ Writing them to both the data disk and a mirror disk .
➢ The controller uses either the data drive or the mirror drive for
data recovery.
LEVEL 2 (redundancy through Hamming):
➢ Bit-level striping means that the file is broken into “bit-sized
pieces”.
➢ It uses a Hamming code for error correction.
LEVEL 3 (bit interleaved Parity):
➢ Byte-level striping means that the file is broken into "byte-
sized pieces“.
➢ Written in parallel on two or more drives.
➢ An additional drive stores parity information.
LEVEL 4 (block interleaved Parity):
➢ Block-level striping means that each file is split into blocks of
a certain size .
➢ Allows each member to act independently when only a single
block is requested.
➢ Service multiple read requests simultaneously.
LEVEL 5 (striping with parity):
➢ Most common secure RAID level.
➢ Except that data are transferred to disks by independent read
and write operations.
➢ Instead of a dedicated parity disk, parity information is spread
across all the drives.
RAID Level-10
• Combine Level-0 and Level-1
• Stripe a files data across multiple disks
– gives great read/write performance
• Mirror each strip onto a second disk
– gives the best redundancy
• The most high performance system
• The most expensive system
Conclusion:
➢ Overall it provides systems with a variety of benefits
depending upon the version implemented.
➢ Most users will likely opt to use the RAID 0 for increased
performance without the loss of storage space.
➢ This is primarily because redundancy is not an issue for the
average user.
