RE: DBA Experiences with Oracle and RAID 0+1

Mogens:

    Just let me disagree with you at only one point. According to my experience, I think that the size of the disks in an array does matter sometimes. It's not the same to have 24 9GB disks that to have only 3 of 73GB. You have 24 spindles againts 3, the first option (in a well configured system of course) will give you better performance in enviroments where you have a lot of concurrency and many users.

    However I think that what I've written above might not be correct (may be it should be tested) if the 73GB outstands for a long way the 9GB disks in terms of seek time and transfer rate.

    Take a look at an extract of Gaja's paper "Implementing RAID on Oracle":

"5) Procure the smallest drive money can buy, keeping in mind scalability, limits of the host
machine, the disk array and growth projections for the database. This is a tough one these
days, with 18 GB drives considered as small drives.

6) Bigger and faster drives are not always better than smaller slower drives, as the seek times
for larger and faster drives with larger form factors, may be more than their smaller and
slower counterparts. This is not that big of an issue, if your drives support a built-in track
buffer cache for storing an entire track's worth of data from read request(s)."

HTH
Greeting
Diego Cutrone

• Original Message ----- To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com> Sent: Tuesday, January 15, 2002 10:25 PM

> Jon,
>
> It's one of those "how many bags will I need in the supermarket?"
> questions - it depends.
>
> Consider:
>
> - RAID 1+0 is much better than 0+1.
> - Three disks is not much w.r.t. IO capability. If you have three
> concurrent users you'll be OK :)
> - Size doesn't matter (who cares if it's 10, 36 or 73 Gig disks? It's
> the IO capabilitity that counts)
> - I'm new to this list, so I don't know if this will work, but I've
> attached a brilliant presentation by our old friend James Morle (check
> out www.ScaleAbilities.com) regarding SAN, NAS and RAS (Random Acronym
> Seminar).
> - If you're only striping across three disks (is that really a SAN?)
> just SAME (Stripe And Mirror Everything). It might not be good, but it's
> simple.
>
> Jon Behnke wrote:
>
> >We are in the process of setting up a SAN using RAID 0+1 for our
database.
> >In our current environment, we are able to separate our tables, indexes,
> >rollback segments, and archive logs on different disks. On the SAN we
would
> >have six 73 gig disks on RAID 0+1 for a total of about 210 Gig of usable
> >space (3 disks worth of space).
> >
> >Some white papers that I have read suggest attempting to separate the
data,
> >indexes, and rollback segments on separate RAID volumes, and others
simply
> >suggest that the performance boost of striping will supercede the
separation
> >of these items.
> >
> >Can anyone offer any comments or suggestions?
> >
> >Jon Behnke
> >Applications Development Manager
> >Industrial Electric Wire & Cable
> >Phone (262) 957-1147 Fax (262) 957-1647
> >jonb_at_iewc.com
> >
>
>
>

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-- 
Author: Diego Cutrone
  INET: dcutrone_at_afip.gov.ar

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