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Donald K. Burleson

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Oracle Redundant Arrays of Inexpensive Disks (RAID)

RAID0/1. Combination of RAID0 and RAID1. May also be called RAID10 depending on whether they are striped and mirrored or mirrored then striped. It is generally felt that RAID10 performs better than RAID01.

RAID2. Data is distributed in extremely small increments across all disks and adds one or more disks that contain a Hamming code for redundancy. RAID2 is not considered commercially viable due to the added disk requirements (10 to 20 percent must be added to allow for the Hamming disks).

RAID3. This also distributes data in small increments but adds only one parity disk. This results in good performance for large transfers; however, small transfers show poor performance.

RAID4. In order to overcome the small transfer performance penalties in RAID3, RAID4 uses large data chunks distributed over several disks and a single parity disk. This results in a bottleneck at the parity disk. Due to this performance problem, RAID4 is not considered commercially viable. RAID3 and -4 are usually are used for video streaming technology or large LOB storage.

RAID5. This solves the bottleneck by distributing the parity data across the disk array. The major problem is that it requires several write operations to update parity data. That said, the performance hit is only moderate, and the other benefits may outweigh this minor problem. However, the penalty for writes can be over 20 percent and must be weighed against the benefits.

RAID6. This adds a second redundancy disk that contains error-correction codes. Read performance is good due to load balancing, but write performance suffers because RAID6 requires more writes than RAID5 for data update.
 

This is an excerpt by Mike Ault’s book “Oracle Administration & Management”.  If you want more current Oracle tips by Mike Ault, check out his new book “Mike Ault’s Oracle Internals Monitoring & Tuning Scripts” or Ault’s Oracle Scripts Download.

 

 ”call

  
 

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