RAIDRAID

CS147 CS147 Dr. Sin-Min LeeDr. Sin-Min Lee

By Kenneth ChenBy Kenneth Chen

HistoryHistory

Norman Ken Ouchi at IBM was awarded Norman Ken Ouchi at IBM was awarded U.S. Patent 4,092,732 titled "System for reU.S. Patent 4,092,732 titled "System for recovering data stored in failed memory unit" covering data stored in failed memory unit" in 1978in 1978In 1987, RAID levels 1 through 5 were forIn 1987, RAID levels 1 through 5 were formally defined by David A. Patterson, Garth mally defined by David A. Patterson, Garth A. Gibson and Randy H. Katz in the paper, A. Gibson and Randy H. Katz in the paper, "A Case for Redundant Arrays of Inexpens"A Case for Redundant Arrays of Inexpensive Disks (RAID)"ive Disks (RAID)"

About RAIDAbout RAID

Early disk drives were costly and bulkyEarly disk drives were costly and bulky

They required strict environmental controlThey required strict environmental control

Solution: RAID -- It stands for “Redundant Solution: RAID -- It stands for “Redundant Array of Independent DisksArray of Independent Disks

Idea: Link up a bunch of small, Idea: Link up a bunch of small, inexpensive disk. Also often referred to as inexpensive disk. Also often referred to as JBOD (just a bunch of disks)JBOD (just a bunch of disks)

Many different RAID method existsMany different RAID method exists

RAID LEVEL 0RAID LEVEL 0RAID 0 implements data strippingRAID 0 implements data stripping

Pro: Least cost, very fast on read and writePro: Least cost, very fast on read and write

Con: Not reliable, no-fault toleranceCon: Not reliable, no-fault tolerance

RAID 1RAID 1RAID 1 implements data mirroringRAID 1 implements data mirroring

Pro: Excellent Protection against crashingPro: Excellent Protection against crashing

Con: Slow on write, costly and inefficientCon: Slow on write, costly and inefficient

RAID 2RAID 2

RAID 2 implements bit stripping with ECCRAID 2 implements bit stripping with ECCPro: Good performance on both read and write. Pro: Good performance on both read and write. Good protection. Cheaper than RAID 1Good protection. Cheaper than RAID 1Con: Hamming code generation is slow, still Con: Hamming code generation is slow, still expensive, no commercial useexpensive, no commercial use

RAID 3RAID 3

RAID 3 implements bit stripping with parity diskRAID 3 implements bit stripping with parity disk

Pro: Very good performance on read, write. Pro: Very good performance on read, write. Good protection. Efficient.Good protection. Efficient.

Con: Complicated controller design. Con: Complicated controller design.

RAID 4RAID 4

RAID 4 implements data stripping with parity RAID 4 implements data stripping with parity drive.drive.Pro: fast on read. Good protectionPro: fast on read. Good protectionCon: VERY slow write speed. Difficult data Con: VERY slow write speed. Difficult data rebuild. Complex design. Not used in real liferebuild. Complex design. Not used in real life

RAID 5RAID 5RAID 5 implements data stripping with distributed RAID 5 implements data stripping with distributed parity parity

Pro: Fastest read speed, decent write speed. Good Pro: Fastest read speed, decent write speed. Good protection. Cost effective = commercial successprotection. Cost effective = commercial success

Con: Most complex design. Difficult to rebuilt data.Con: Most complex design. Difficult to rebuilt data.

RAID 6RAID 6

RAID 6 implements data stripping with dual error RAID 6 implements data stripping with dual error protectionprotectionPro: Excellent protection, can sustain multiple Pro: Excellent protection, can sustain multiple hits.hits.Con: Complex to implement. Con: Complex to implement.

RAID 10RAID 10RAID 10 = 1 + 0 implements data stripping with RAID 10 = 1 + 0 implements data stripping with mirror drive.mirror drive.

Pro: Excellent protection. Good read and write Pro: Excellent protection. Good read and write speed compare to other.speed compare to other.

Con: Very expensive.Con: Very expensive.

RAID DPRAID DP

RAID DP = Double Parity implements data RAID DP = Double Parity implements data stripping with dual parity disks. stripping with dual parity disks.

Pro: Excellent protection. Reasonable cost.Pro: Excellent protection. Reasonable cost.

Con: Performance not as good as RAID 5.Con: Performance not as good as RAID 5.

More on RAIDMore on RAID

Textbook page 364-376Textbook page 364-376

http://www.acnc.com/raid.htmlhttp://www.acnc.com/raid.html

http://en.wikipedia.org/wiki/Redundant_arrhttp://en.wikipedia.org/wiki/Redundant_array_of_independent_disksay_of_independent_disks

THANK YOU!!!! THANK YOU!!!! And sorry for the boring presentation -_-And sorry for the boring presentation -_-