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

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