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Info: What Are The Different Types Of RAID?

post #1 of 16
Thread Starter 
Straight to the FAQ.

RAID stands for Redundant Array of Independent (or Inexpensive) Disks, a category of disk drives that employ two or more drives in combination for fault tolerance and performance. RAID disk drives are used frequently on servers but aren't generally necessary for personal computers.

There are number of different RAID levels:
  • Level 0
  • Level 1
  • Level 2
  • Level 3
  • Level 4
  • Level 5
  • Level 6
  • Level 0+1
  • Level 10
  • Level 7
  • Level 50
  • RAID S

Level 0:

Level 0 is a 'striped' disk array without fault tolerance. It provides data striping (spreading out blocks of each file across multiple disk drives) but no redundancy. This improves performance but does not deliver fault tolerance. If one drive fails then all data in the array is lost.



Level 1:

Level 1 does 'mirroring' and 'duplexing'. It provides disk mirroring. Level 1 provides twice the read transaction rate of single disks and the same write transaction rate as single disks.



Level 2:

Level 2 does 'error-correcting coding'. It isn't a typical implementation and rarely used. Level 2 stripes data at the bit level rather than the block level.



Level 3:

Level 3 is 'bit-interleaved parity'. It provides byte-level striping with a dedicated parity disk. Level 3, which cannot service simultaneous multiple requests, also is rarely used.



Level 4:

Level 4 is 'dedicated parity drive'. It is a commonly used implementation of RAID. Level 4 provides block-level striping (like Level 0) with a parity disk. If a data disk fails, the parity data is used to create a replacement disk. A disadvantage to Level 4 is that the parity disk can create write bottlenecks.



Level 5:

Level 5 is 'block interleaved distributed parity'. It provides data striping at the byte level and also stripe error correction information. This results in excellent performance and good fault tolerance. Level 5 is one of the most popular implementations of RAID.



Level 6:

Level 6 is 'independent data disks with double parity'. It provides block-level striping with parity data distributed across all disks.



Level 0+1:

Level 0+1 is 'a mirror of stripes'. It isn't one of the original RAID levels. Two RAID 0 stripes are created, and a RAID 1 mirror is created over them. Used for both replicating and sharing data among disks.



Level 10:

Level 10 is 'a stripe of mirrors'. It isn't one of the original RAID levels. Multiple RAID 1 mirrors are created, and a RAID 0 stripe is created over these.



Level 7:

Level 7 is a trademark of "Storage Computer Corporation" that adds caching to Levels 3 or 4.



Level 50:

Quote:
RAID 50 should really be called "RAID 03" because it is implemented as a striped (RAID level 0) array whose segments are RAID 3 arrays. RAID 50 has the same fault tolerance as RAID 3 as well as the same fault tolerance overhead. High data transfer rates are achieved thanks to its RAID 3 array segments. High I/O rates for small requests are achieved thanks to its RAID 0 striping. Maybe a good solution for sites who would have otherwise gone with RAID 3 but need some additional performance boost. Very expensive to implement. All disk spindles must be synchronized, which limits the choice of drives. Byte striping results in poor utilization of formatted capacity.


RAID S:

RAID S is "EMC Corporation's" proprietary striped pairty RAID system used in its Symmetrix storage systems.



I hope that this FAQ has helped for decisions and information.

Some pics from www.acnc.com

By Christian Somody (somody)
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post #2 of 16
Good visuals .. point on the RAID-1 - true this is a mirror of drives but where the Duplex comes in is if the RAID controller is duplicated which is generally why it is only seen in server systems rather than the home rig.

On RAID-5 while it is true that this is popular, it is so in the server systems and really requires a dedicated controller with its own cache. To implement this on the desktop MB with software is a performance hit that is noticable to the user.
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post #3 of 16
wow... dude this is a awsum faq...

been wandering what raid 50 was thx rep 4 u
post #4 of 16
Link to the site you got those photo's from- I remember seeing them somewhere else.
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post #5 of 16
Thread Starter 
Quote:
Link to the site you got those photo's from- I remember seeing them somewhere else.
Link added...thanks!
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post #6 of 16
I was wanting to know what the different configurations were and which designation meant which. Thanks for creating this FAQ!
    
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post #7 of 16
Thread Starter 
Quote:
I was wanting to know what the different configurations were and which designation meant which. Thanks for creating this FAQ!
no prob!!
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post #8 of 16
Good FAQ
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post #9 of 16
Thread Starter 
Quote:
Good FAQ
thanks
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post #10 of 16
woah... that musta been an alnighter, unless u ripped it all Good job, thnx
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