On Jul 26, 2006, at 8:39 AM, Brian France wrote:
Folks, I have an image that is 1280m. It's swap space is 464m. Is that a good ratio? The image has chewed up according to Perftoolkit 75% of it. I was thinking a bigger swap space as opposed to more memory which is what I being pressured to do. Response times seems great. This image is running DB2 and Tamino (SAG data base) and some other things. I just was sure if there was a good rule of thumb to follow regarding image size and swap space. THANX!!!
I like to have swap as big as physical memory, or on some servers twice its size. However, what I'd really recommend: make your image big enough that it's just barely swapping. Then define multiple tiers of swap. The highest (lowest? I can never remember how swap priority works without the man page)--anyway, the one you swap to first should be on VDISK or a saved segment mapped into your address space, and should be somewhere around 25% of physical memory--and beyond that, have real DASD for swap backing. Sine Nomine has a free program called SWAPGEN that you can download that does all the work of allocating and writing a swap signature to VDISK during your initial CMS IPL of the guest, which makes that approach very easy (although it's a bit slower than saved-segment- mapped swap, I think). In general. Your mileage may vary, this is only a rule of thumb and depends on your actual workload, etc., etc....but that's where I'd start. Adam ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390
