Re: RE: Cook device vs Raw device

How are you accessing the raw device, as a raw disk or a raw logical volume. As a raw logical volume all access must be in 512 byte blocks or it'll run very poorly. If it is as a real raw disk there should be no other logical volumes on any part of the disk. You might like to check the min/max servers side of AIO. Are you using IBM disks, if not then changing the q_type to simple and alternating the queue_depth to 3 should help IBM provide a performance package makes life a lot easier, the one on the OS distribution is incorrect, you need to get the correct one from the IBM web site ( I think it's the Austen one). If you can't find it come back to me I'll send the copy over and a couple of data collection scripts. Rather than using iostat you need to be using filemon, it give a much more detailed breakdown of what is going on. Paul Watson WF Software Ltd Tel: +44 1436 674729 Fax: +44 1436 678729 www.wfsoftware.com/informix # If you broke it, hide the evidence >>> William Rice <ricew@operamail.com> 09/15/99 09:01PM >>> This is a thread that has always interested me. I have been reading this group for awhile, and was concerned when I came to my current place of employment and discovered they were using filesystems to hold data. When we got the oppurtunity to do some limited testing on raw vs cooked we could only find at most a 1.5% difference between informix's performance to raw disk vs. cooked. We watched the following things: iostat, vmstat wall time We were running AIX 4.3.2 on a 520 Informix 7.31UC2 Only 2 disk drives, one of which was dedicated to informix data. Under 2 Gigabytes of data in the whole database These processes were simple queries(no more than three tables joined) and the loading of data into tables. The longest running process was somewhere around 15 minutes. The processes tested caused the system to be heavily io bound for some and CPU for others. From reading the newsgroup I got the impression that I could count on at least a 10% difference between cooked and raw, yet the tests I ran did not turn out that way. The data involved was literally identical. I was curious what factors might be causing the performance not to increase. Will ------------------------------------------------------------ This e-mail has been sent to you courtesy of OperaMail, a free web-based service from Opera Software, makers of the award-winning Web Browser - http://www.operasoftware.com ------------------------------------------------------------ ********************************************************************** This email and any files transmitted with it are confidential and intended solely for the use of the individual or entity to whom they are addressed. If you have received this email in error please notify the system manager. This footnote also confirms that this email message has been swept by MIMEsweeper for the presence of computer viruses. www.mimesweeper.com **********************************************************************