IDS Forum

Re: Informix Chunk Size - 1 big or manysmaller

Posted By: Art Kagel
Date: Wednesday, 31 March 2010, at 10:39 p.m.

In Response To: RE: Informix Chunk Size - 1 big or manysmaller (Chin, Paul (TSG-OSDO))

If you are talking about multiple chunks on a single spindle, you may be
correct, however, if the chunks are allocated from a RAID array located on a
SAN with extensive non-volatile cache memory, then you can absolutely push
more data down to it than a single thread can handle. And again, how many
threads and how much data will choke the cache and revert to slower
behavior, will depend on your configuration, so YMMV and back to the
trade-offs.

Art

Art S. Kagel
Advanced DataTools (www.advancedatatools.com)
IIUG Board of Directors (art@iiug.org)

See you at the 2010 IIUG Informix Conference
April 25-28, 2010
Overland Park (Kansas City), KS
www.iiug.org/conf

Disclaimer: Please keep in mind that my own opinions are my own opinions and
do not reflect on my employer, Advanced DataTools, the IIUG, nor any other
organization with which I am associated either explicitly, implicitly, or by
inference. 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, Mar 31, 2010 at 9:31 PM, Chin, Paul (TSG-OSDO) <pchin@hp.com> wrote:

> Wouldn't IO speed would ultimately determine the flush time? IF 5
> thread/chunk
> writing to the same disk or striped disk, wouldn't it be the same as 1
> thread/chunk?
>
> I believe unless the chunk are in different disk it wouldn't make any
> differece.
>
> Paul
>
> -----Original Message-----
> From: ids-bounces@iiug.org [mailto:ids-bounces@iiug.org] On Behalf Of Art
> Kagel
> Sent: Thursday, 1 April 2010 12:18 PM
> To: ids@iiug.org
> Subject: Re: Informix Chunk Size - 1 big or manysmaller [19477]
>
> It is a balance, as in most things. At checkpoint time the engine assigns
> chunks to CLEANER threads so the more chunks you have the more processes
> you
> will have flushing your data to disk in parallel to minimize checkpoint
> time
> and impact on the system. Longer checkpoints also may mean more data at
> risk
> or longer recovery times if the server crashes during a checkpoint. On the
> other hand, the fewer chunks you have the easier it is to manage the
> server.
> Tradeoffs and no hard rules.
>
> Art
>
> Art S. Kagel
> Advanced DataTools (www.advancedatatools.com) IIUG Board of Directors
> (art@iiug.org)
>
> See you at the 2010 IIUG Informix Conference April 25-28, 2010 Overland
> Park
> (Kansas City), KS www.iiug.org/conf
>
> Disclaimer: Please keep in mind that my own opinions are my own opinions
> and
> do not reflect on my employer, Advanced DataTools, the IIUG, nor any other
> organization with which I am associated either explicitly, implicitly, or
> by
> inference. 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, Mar 31, 2010 at 3:04 PM, Wyza, Jonathon
> <wyzaj@bethelcollege.edu>wrote:
>
> > This question was posted by someone on the list serve for the product
> > I work with, but there hasn't been much of a response. I was hoping
> > someone could answer the below as I'm interested in this as well.
> > (note that this will relate to a SLES 11x64 IDS 11.50 box)
> >
> > I'm looking for opinions (facts acceptable too).
> >
> > We are in the hardware and disk layout phase of preparing for CX on
> Linux.
> > I
> > look at our current system and see 5 chunks for our cars database
> dbspace.
> > They are each 2 GB for a total of 10GB.
> >
> > My question is:
> > Should I set the new server up with one big chunk (~20GB) or break it
> > up into more smaller chunks?
> >
> > Research:
> > I have been searching for an answer to this question and do not find
> > much guidance. I found that there used to be a 2GB size limit on a
> > single chunk until Informix 9.4. There also used to be a limit on the
> > number of chunks around 4000. I think the new limit on the number of
> > chunks is 32766. I found one page that said with multiple chunks there
> > are multiple threads to flush changes to disk so it takes less time to
> > flush changes. There is an SAP tuning page that states that the ideal
> > number of chunks for a dbspace is 1. Other than that don't have too
> > much info.
> >
> > I would love to hear any opinions (or facts).
> >
> > Sean
> >
> > Jonathon Wyza
> > CX & CBORD System Administrator
> > CX Programmer/Analyst
> > Administrative Computing
> > Bethel College
> > (574)-257-3381
> > AIM: Iamwyza
> > jonathon.wyza@bethelcollege.edu<mailto:jonathon.wyza@bethelcollege.edu
> > >
> > ==============================
> > SLES 10x32 SP2 & IDS 10.00.UC9
> >
> > " I would love to change the world, but they won't give me the source
> > code."
> > -- Unknown
> >
> >
> >
> >
>
>
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> >
> >
>
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>
>
>
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>
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>
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Messages In This Thread

• Informix Chunk Size - 1 big or manysmaller
  Wyza, Jonathon -- Wednesday, 31 March 2010, at 3:04 p.m.
  • Re: Informix Chunk Size - 1 big or manysmaller
    Lennie Jarratt -- Wednesday, 31 March 2010, at 3:09 p.m.
  • Re: Informix Chunk Size - 1 big or manysmaller
    Art Kagel -- Wednesday, 31 March 2010, at 9:17 p.m.
    • RE: Informix Chunk Size - 1 big or manysmaller
      Chin, Paul (TSG-OSDO) -- Wednesday, 31 March 2010, at 9:31 p.m.
      • Re: Informix Chunk Size - 1 big or manysmaller
        Art Kagel -- Wednesday, 31 March 2010, at 10:39 p.m.

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