On Thu, Mar 20, 2008 at 3:09 PM, Harris, Nick J. <[EMAIL PROTECTED]> wrote: > All very good points. We do have a good monitor we just need to learn > how to use it and what to look for. It will just take time.
I think it is good to look at your configuration and estimate how many more you could run without hurting yourself. Or to look at your deployment plans and come up with an estimate of how many IFLs you would need to get. Your own Linux servers are the best ones to compare... Look at your overall utilization breakdown and see how many % of a CPU each Linux uses. With Linux on z/VM, the low-hanging fruit is the servers that are under-utilized. When they are used only 5% of the time, you could in theory have 20 of them on a single CPU. Obviously when two servers want their share at the same moment, they would be competing and get delayed. Not as bad as you would fear because many applications have periods where they don't use much CPU, even when they are busy (because they do disk I/O or wait for network data). And this works out better with many CPUs and many Linux servers. But even with a few dozen, you want to look at their idle usage. When the Linux server has all kind of other good stuff in addition to running your application (like checking for software updates, keep active agents running, etc) then that "idle load" does start to count. With 20 servers using 2.5% of a CPU when idle, you already use half a CPU. That means the business workload must do with just the other half. The lower you get their CPU usage in idle periods, the better. It is not uncommon to have the idle server use less than 0.5% of a CPU when you have stopped various useless background noise. Often the next issue is memory usage. When your your Linux server is idle for a longer period, z/VM should be able to take away some of the memory resources and give it to the servers that are busy at that time. Much of that comes from proper sizing, and also making sure they get really idle (so z/VM will notice that and take resources away). If you're into this, performance classes and conferences are probably worth the investment. Rob -- Rob van der Heij Velocity Software GmbH http://velocitysoftware.com/
