Fw: AIO VP's -how many?

["Vasyl Shulzhenko" <vasilis@softline.kiev.ua>]

----- Original Message -----
From: Art S. Kagel <kagel@bloomberg.net>
Newsgroups: comp.databases.informix
To: <CKGeier@nwc.edu>
Sent: 31 ЛЮЪ 2000 Ц. 20:29
Subject: Re: AIO VP's -how many?


> These are all good rules of thumb some of which (like ==#CPUS and
==#disks)
> will give you starting values while others (like -g ioq and -g iov) give
> you monitoring techniques to tune the number of AIO VPs.  The rules of
> thumb that I use are thus:
>
> Initial # AIO VPs:
>
> IDS Version      # VIO VPS
> ------------     ----------
> 7.1x 2.5 * # chunks (or use disks if discrete disks chunks if
> 7.20-7.23 2.0 * # chunks (chunks are part of disk arrays
> 7.24, 9.1x 1.5 * # chunks
> 7.3x, 9.2x 1.0 * # chunks + 2-4 for overhead
>
> Monitoring:
> onstat -g iov and look at io/wkup.  If ALL AIO VPS have io/wkup >= 1.0
> then you probably can benefit from more AIO VPS.  There should always
> be at least one AIO VP with io/wkup <1.0 indicating that often it was
> awakened and another AIO VP had already accepted the job so there was
> nothing to do.
>
> In addition monitoring the queue lengths of the chunks (-g ioq) and the
> VPS themselves (-g iov) will also clue you in to a need for more VPS.
>
> Art S. Kagel
>
> CKGeier@nwc.edu wrote:
> >
> > We are using AIX 4.3.3, and IDS 7.31UC3, with 2 processors but
> > MULTIPROCESSOR=0, so we are using one CPU VP. I have 2 AIO VP's
> > configured. We are not using kaio as it caused Informix crashes when we
> > implemented a web server to access the Informix database.
> >
> > I have heard differing ideas about how to configure AIO VP's. I have
> > looked at "onstat -g ioq" which shows me quite consistently an aio len
of
> > 0 and maxlen of 1. One book I have read, "Informix Performance Tuning"
by
> > Elizabeth Suto says to use this command to see if there are many
requests
> > in the aio queue. So my results seem to suggest that it probably isn't
> > necessary to add more aio vp's. However, I have also heard that I should
> > look at "onstat -g iov" and look at io/s and ours shows around 30 - this
> > would suggest that we should have more than 2 AIO VP's.
> >
> > AND I have also read in other books that the number of AIO VP's should
be
> > equal to the same number of CPU VP's  (one)
> >
> > AND I have also read in more books that AIO VP's should be equal to the
> > number of disks that I/O is being performed on. That seems to suggest we
> > should be using 6 of them.
> >
> > SO.....the truth is out there......Do you know how I find it or what it
> > is?
> >
> > Cathy Geier
> > Unix/Web/DB Admin
> > Northwestern College
> > St. Paul, MN
> > 651-631-5284