> Thanks for all your answers. I guess I'll give him another vdisk of 4G and if > he > needs more, I can "swapgen" another vdisk.
Yeah, small incremental increases usually are good thing. > Is one 8G swap device better than 4 2G swap devices ? It's a lot easier adding > another swap device than having to increase an existing swap. Since there can be only one outstanding I/O for a device number in the s390x architecture (putting PAV aside, since it doesn't apply to VDISK), having more than one device _usually_ works better. VDISK is really, really fast, but having options for Linux to initiate multiple page I/O requests can help. One pattern I've seen used repeatedly is: 3 swap disks in priority order (see the man page for swapon): 1. VDISK half size of main memory 2. VDISK size of main memory 3. Real MDISK size of main memory. The VDISKs don't take up space unless they're actually used. You monitor swap usage, and if you ever get more than half way into the 2nd VDISK, time to up main memory size. If you get into the real MDISK, things will get really icky really fast -- something your automation should be checking. Keep an eye on the amount of VM paging space you have allocated too -- if you get a workload spike with lots of VDISK active, that's where it comes from, and if you run out, Bad Things happen. A good target is to have VM page space about 50% full at max, again multiple smaller devices may perform better than larger devices. ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 ---------------------------------------------------------------------- For more information on Linux on System z, visit http://wiki.linuxvm.org/
