On Dec 3, 2007 7:13 AM, Leland Lucius <[EMAIL PROTECTED]> wrote: > But, I like a little excitement every so often, so I got this crazy idea to > replace all secondary swap with VDISK and just boost up the VM paging > volumes.
That seems like a good idea to me. But what else can I say, since we have been promoting this for a while. As long as a VDISK does not get used, the cost is neglectable. When you set up proper monitoring to detect when it gets used, you could get away with less than the maximum amount of paging space for VM. > We don't actually hit Linux swap all that much so probably 15% or so of that > 275GB is ever really in use. (Yes, I know...we're probably oversizing our > guests, but that's a different story.) > I know I'd have go boost up the number of paging volumes, but does VM have > to map all of that storage even if it doesn't get used? You need to provide enough z/VM paging space for what is being used. And we say ideally a factor 2 over that to allow for efficient paging. If you have 15% of the 275G in use at 50% full, then one or two servers misbehaving would not yet cause you too much trouble. But do monitor it. If you don't monitor you must provide space for what might possibly get used (which is 6 times as much in your case). Because of the Linux algorithm for using swap, a VDISK used for swap even a little will eventually be used completely. So you need to prepare for all of these disks to end up in z/VM paging space. If you see z/VM page in your VDISK on a constant basis, you should look at making the VDISK smaller. Rob -- Rob van der Heij Velocity Software, Inc http://velocitysoftware.com/
