RE: Dirty page queues during a checkpoint (WAS: The old raw devic

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 sending to informix-list