Re: Async I/O on AIX

"Chuck" <chuckh_at_softhome.net> wrote in message news:<am7fea$3aun4$1_at_ID-85580.news.dfncis.de>...
> "tingl" <tlam15_at_hotmail.com> wrote in message
> news:f487699f.0209161411.4fd16379_at_posting.google.com...
> > "Chuck" <chuckh_at_softhome.net> wrote in message
> news:<am537c$2pm0o$1_at_ID-85580.news.dfncis.de>...
> > > -----BEGIN PGP SIGNED MESSAGE-----
> > > Hash: SHA1
> > >
> > > The Oracle 8i Administrator's Reference for AIX says to set the max
> > > i/o servers to "at least 10*(number of disks that AIO accesses
> > > simultaneously)". Can someone clarify whether they mean physical
> > > disks, or logical filesystems? TIA
> > >
> > > -----BEGIN PGP SIGNATURE-----
> > > Version: PGPfreeware 7.0.3 for non-commercial use <http://www.pgp.com>
> > >
> > > iQA/AwUBPYYQJFVYIIV9CtSHEQLgTQCfRljaHtVp1TkI1R/2Ng6/T1Kv6lYAn1w4
> > > zWexcehNN+v3YhQEBkNXId/S
> > > =mzUG
> > > -----END PGP SIGNATURE-----
> >
> > Physical disks.
>
> Just to be sure then, if I have 15 file systems that are concurrently in
> use, each of which is a 3 volume RAID logical device, I need 450 async i/o
> servers. Is that correct? It just seems like an awful lot.
>
> TIA
Yes, it does seem like a large number. This is only provided as a guideline. Actual usage may vary from system to system. You have to experiment a little.

For example, you could set max_aios to 450 and min_aios to 200. When your system starts, it will start 200 aios and the number increases on demand up to max_aios. After a period of time, you can issue this command to see the peak number of aios started since the system reboot.

pstat -a |grep aio|wc -l

It should give you an idea how many aios you need. Make sure you don't run low on memory.

Tony Received on Tue Sep 17 2002 - 14:07:11 CDT