IDS Forum

Re: Informix page cleaners (w/ a SAN)

Posted By: Art Kagel
Date: Friday, 17 April 2009, at 10:32 a.m.

In Response To: Informix page cleaners (w/ a SAN) (James Maes)

There are other competing recommendations also. You should have at least as
many CLEANERS and LRUS (or the total of all lru parameters in all of the
BUFFERPOOL settings). Another is one per physical disk (with SANS and other
large arrays that one has gotten mostly deprecated.) The bottom line is
that you need enough CLEANER threads running to efficiently flush all dirty
buffers without affecting production be blocking code from entering critical
sections during checkpoints for too long.

At checkpoint time that means one cleaner per chunk as checkpoint writes are
assigned to cleaners by chunk. This is the one that allows only half that
number if there are lots of chunks and especially if they all reside on one
or a few physical structures to minimize the possibility that you will be
limited by the bandwidth of the strucuture or its channels. At LRU flush
time (LRU_MIN/MAX_DIRTY) you need at least one CLEANER per LRU queue because
dirty pages are assigned to cleaners by LRU queue. Again, on a moderately
busy system with only a few structures you can get away with half that
number for the same reasons and also because on average only half of the LRU
queues will reach LRU_MAX_DIRTY at any given time. However, if the system
is typically busy enough to cause all of the LRU queues to reach the
LRU_MAX_DIRTY threshold at the same time, then you will need more CLEANERS.

Art S. Kagel
Oninit (www.oninit.com)
IIUG Board of Directors (art@iiug.org)

Disclaimer: Please keep in mind that my own opinions are my own opinions and
do not reflect on my employer, Oninit, the IIUG, nor any other organization
with which I am associated either explicitly or implicitly. Neither do
those opinions reflect those of other individuals affiliated with any entity
with which I am affiliated nor those of the entities themselves.

On Wed, Apr 15, 2009 at 3:28 PM, James Maes <jmaes@materialogic.com> wrote:

> We have read some tuning recommendations that seem to indicate that for IDS
> 10:
>
> If you have fewer than 20 disks you should use 1 cleaner/disk
> With 20 - 100 disks you should set 1 cleaner for every other disk.
>
> (We are currently set to 128)
>
> We run on HPUX 11 (PA-RISC) connected to an older HP Fiber SAN exposed to
> us
> as 90 to 100 LUNS (which are used as raw chunks for the dbspaces).
>
> Could anyone give a recommendation on how, if at all, the above
> recommendation would fit into an environment like ours?
>
> Thanks
> -JM
>
> James Maes | Software Architect | Main: 314.997.1854 ext. 3422 |
> Materialogic – Your Supply Chain’s Strongest Link | www.materialogic.com
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Messages In This Thread

• Informix page cleaners (w/ a SAN)
  James Maes -- Wednesday, 15 April 2009, at 3:28 p.m.
  • Re: Informix page cleaners (w/ a SAN)
    DAVORIN KREMENJAS -- Thursday, 16 April 2009, at 7:24 a.m.
    • RE: Informix page cleaners (w/ a SAN)
      James Maes -- Thursday, 16 April 2009, at 6:50 p.m.
      • Re: RE: Informix page cleaners (w/ a SAN)
        DAVORIN KREMENJAS -- Friday, 17 April 2009, at 5:45 a.m.
  • Re: Informix page cleaners (w/ a SAN)
    Art Kagel -- Friday, 17 April 2009, at 10:32 a.m.

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