RE: Dirty page queues during a checkpoint (WAS: The old raw devices chestnut)

#1 (**permalink**) 04-19-2008, 10:05 PM

Thanks Bill,

Found it in 7.3 manual also, p 11-53, identical paragraph as in 9.4
manual:

"During a chunk write, each page-cleaner thread is assigned to one or
more
chunks. Each page-cleaner thread reads through the buffer headers and
creates an array of pointers to pages that are associated with its
specific
chunk."

> -----Original Message-----
> From: Bill Dare [mailto:dareb@jevic.com]
> Sent: 16 April 2004 15:22
> To: Willem Roos; informix-list@iiug.org
> Subject: RE: Dirty page queues during a checkpoint (WAS: The
> old raw devices chestnut)
>
>
> http://publibfi.boulder.ibm.com/epubs/pdf/ct1ucna.pdf
>
> Page 7-44 for chunk writes, which are the type of writes that are done
> during page flushing.
>
> Regards,
> Bill
>
>
> > -----Original Message-----
> > From: Willem Roos [SMTP:wroos@shoprite.co.za]
> > Sent: Friday, April 16, 2004 5:13 AM
> > To: informix-list@iiug.org
> > Subject: Dirty page queues during a checkpoint (WAS: The old raw
> > devices chestnut)
> >
> > This horse is nearly dead now, but I do have one more question, if i
> > may:
> >
> > When pages are queued for flushing to disk during a
> checkpoint, how is
> > it queued? Is there a queue per chunk, or is there a queue
> per dbspace,
> > or am i completely wrong here? And may this affect performance?
> >
> > The reason i ask is because i've noticed that I/O sometimes
> peters out
> > as the checkpoint progresses. I know this because i run
> onstat -P every
> > so many seconds and sometimes you can see later in the
> checkpoint that
> > there are dirty pages outstanding for one large table only
> (which has
> > its own dbspace). Has anybody seen this (apparent) behaviour?
> >
> > Then i must say that I do hate this checkpoint business. Or beter, i
> > hate the fact that Informix blocks during a checkpoint.
> This particular
> > feature of Informix has elevated the art of checkpoint
> duration tuning
> > to something close to black magic. I can't think of any other dbms's
> > that do that - blocking i mean.
> >
> > Lastly, i think with the (very fast) growing trend towards
> > virtualization of storage (on the hardware and software layers) that
> > fs-vs-raw should eventually become a moot issue. I mean, at
> one point in
> > time we ran our database off a Netapp filer (and therefore
> on NFS), and
> > what a brilliant piece of storage virtualization that is!
> >
> > Just my 6 cents.
> >
> > -------------------------------------------
> > Willem Roos - (+27) 21 980 4941
> > Per sercas vi malkovri
> >
> > > -----Original Message-----
> > > Removed for brevity
> >
> > sending to informix-list
>

Disclaimer
http://www.shoprite.co.za/disclaimer.html

sending to informix-list

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode