Re: HELP: Info about ORACLE7 Performance on RAID

Will Kooiman, kooiman_at_interserv.com wrote: Will,

I respected your email inputs. However, your RAID definitions are wrong.

RAID 0: striping but has no parity (i.e. no redundancy). Lose a disk in the raid,

        lose the whole raid (rank). I/O is as fast as a regular disk (if not faster). RAID 1: mirror disk. Lose a disk, still okay. I/O is as fast as a regular disk. RAID 5: striping with parity. Lose a disk in the raid, still okay but the raid will

        be operated in degrade mode. If lose two or more disk in the rank, the 
        whole rank is gone. Slower on write compares to regular disk because 
        RAID-5 needs to recompute parity on each write.

Note: RAID technology allows hot replacement and disk reconstruction (replace
      the bad disk and then rebuild the raid) on line (i.e. while the RAID disk 
      subsystem is active).

-Ted.

>Quick RAID overview:
>
>Without going into a lot of detail, here's the scoop on the most popular RAID levels.
>
>RAID 0 (mirroring) reads are slightly faster, writes are slightly slower (with redundancy)
>RAID 1 (striping) reads are much faster, writes are much faster (no redundancy)
>RAID 0+1 reads are much faster, writes are much faster, (with redundancy)
>RAID 5 reads are much faster, writes are much slower (with redundancy)
>
>
>Hope this helps,
>Will Kooiman
>
>

-- 
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= Theodore Do                               =
= Senior Technical Specialist, UNIX/ORACLE  =
= TRW Information Technology                =
= tdo_at_mailsrv1.trw.com                      =
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