Re: Multiple LUNs vrs one large stripe. Opinions?

From: computer person (fake_address_at_nothing.com)
Date: 12/14/03 

Date: Sun, 14 Dec 2003 12:52:33 GMT

"Beeblebrox" <sl1433@hotmail.com> wrote in message
news:c976cb73.0312132303.11e72736@posting.google.com...
> I'm in the process of building some new servers, and I'm debating a
> storage configuration issue. We'll likely use 3310s as our solution
> (although that's not terribly relevant. The alternative is a similar
> type storage device). These Solaris 8, V480 hosts will have Oracle
> running on them.
>
> Should I set up 1 large oracle data filesytem or multiple filesytems
> (each with it's own lun, as a result)?
>
> The large filesystem's advantage is:
>
> 1) simplicity for sysadmins and dbas. Just 1 filesystem to contain
> the datafiles and indexes, so no need to try manually balancing space
> and performance between filesystems;
>
> 2) many more members in the stripe, so IO can be spread across more
> disks;
>
> The more-luns advantage is:
>
> 1) less likely to hit a LUN queue depth limitation (which of course
> affects Disk IO performance);
>
> 2) if we need to fsck, a smaller filesystem will take less time
> (assuming just 1 of several needed fsck-ing);
>
> I'm leaning towards the 1 large filesystem approach, as it is unclear
> to me if the LUN queue depth issue really exists these days on modern
> hardware. I recall that at a former company I worked for, we needed
> shorter queue depths for systems attached to EMC for some reason, but
> we're not using EMC in this case (or any case).
>
> Thoughts, suggestions, references, or best-practices appreciated.

I am assuming you will be using Veritas Volume Manager/fs. I just finished
the Veritas Foundation Suite 3.5 course and I asked a similar question. The
answer was basically - use multiple luns and do Veritas striping on top of
Hardware mirror-stripe. If you use Raid 5 on the 3310 (avoid if you can)
then the extra software striping will boost performance. If you must go with
a single large lun then use Quick I/O feature (licnesing required). That
gets allows you to avoid double buffering and get you back the Async I/O
benefits (C0IO)

Anyways, thats what they said in the course.. Anyone beg to differ?.

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