Re: Does DB2 really need this many filesystems? (822 in one case)

From: 73blazer (yoyo_at_ma.com)
Date: 12/26/03 

Date: Fri, 26 Dec 2003 14:50:49 -0500

Short answer no.
Better answer, no.
A few filesystems spread over different disks for different parts of the
  DB files, fine, but 822 is, well, way too many. Somewhere around 75
filesystems I've noticed AIX really takes a crap when it comes to a df,
any mount or unmount, even the cdrom, the overhead associated to
maintaining all those filesystems, just from an OS perspective, not
considering the administrator, far exceeds any performance benifit you
would recieve from so many filesystems.
Here's what I do, take a single instance. Say I have 14 tablespaces in
that instance. Say, 3 of them get hit fairly heavily and the rest just
occasionally. I would, make a filesystem for the instance on one disk, a
filesystems for each of the heavily hit tablespaces on different disks,
and put the rest on 1 or two filesystems, on other disks. If your using
an SSA array, well, things are different. Just make the SSA array one
big Volume Group, then make 1 filesystem for all of DB and it's
instances, since the SSA management part of the OS will take of
spreading things accros the disks.

Ken

Tonij wrote:
> Hi all,
>
> We have a few IBM boxes running DB2, some 4.3.3 older boxes and some P
> Series running 5.2
>
> What I have noticed in this environment is the DBAs always ask for
> TONS of filesystems for their databases; when questioned about it we
> are told there is no other way to do it. We have one box that has 822
> (that is not a typo) filesystems! It takes about 15 minutes to unmount
> them all.
>
> Is this common for DB2 or are we stuck in some old fashioned way of
> doing things?
>
> Just curious what other boxes running DB2 look like...

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