Re: DBA Experiences with Oracle and RAID 0+1

Mogens,

In regard to the number of spindles issue: James Morle has some excellent discussion on that in 'Scaling Oracle 8i'. ( I think it's that book )

When some of the newer larges drives are used in a given configuration, they mabe be able to outperform older drives in a similar configuration with a larger number of spindles.

I say 'older' since smaller drives usually aren't using the latest technology and the newer ones have sufficiently higher throughput to match the capability of a larger number of drives in given configuration.

Food for thought, anyway.

Jared

On Sunday 20 January 2002 06:50, Mogens Nørgaard wrote:
> Diego,
>
> I agree with you 100% and didn't express myself correctly in my email.
> The more spindles the better. What I meant to say was that you must
> never buy disks by taking your total needed amount of space and divide
> by the number of big disks you can get hold on :). It's the number of
> IO's required by the disk system that matters, not the size...
>
> Thanks for making this clear to everyone.
>
> Mogens
>
> Diego Cutrone wrote:
> >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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