Xenia, wouldn't it be better if VMRM didn't have to depend on users remembering to do this as their workload changes? If they have one large server say with a large oracle application, the minimum value setting would have to be the minimum for this server? So all servers are treated and trimmed equally. And if the users happen to change their workload (but we know users don't do this), the setting would be changed after the first outage? Our approach is to look in side the server and not depend on a systems staff that must know everything their users are doing. (And yes Mike this could be considered marketing - but what an opportunity)
Xenia Tkatschow wrote:
I'm curious that Barton wrote on August 28th:VMRM has taken so much storage away from servers that the server or application dies. I would HIGHLY recommend against using it.z/VM has recently documented how to keep VMRM from eating up too much memory, though the mechansim to do so has been there since at least 5.2. The z/VM Performance book, Chapter 17 - VMRM Tuning Parameters, talks about a constant MinRequired. MinRequired is the minimum amount of memory the Linux guest(s) must have at all times. VMRM will not ask the guest(s) to shrink beyond that point. Below is the usage note added to Chapter 17 of the z/VM Performance book. 4. Use of VMRM-CMM can potentially reduce the performance of one or more of the participating Linux guests because VMRM can ask the Linux guests to give up too much memory resulting in the Linux guests using excessive CPU time trying to find more storage to give up and leaving little CPU time available for useful work. To prevent this situation from happening, VMRM has a configurable constant that defines a value below which VMRM will not ask the Linux guests to shrink. By default, this safety net value is 64MB, but for certain workloads, the value may be too low, thus causing poor performance. The safety net value is defined by the constant MinRequired in the VMRM constants file, IRMCONS COPY, and by default is set to 16384 pages. To change the safety net value, update the value of constant MinRequired (set in pages) in file IRMCONS COPY. The update should be made as a local modification using the automated local modification procedure documented in Appendix D in the z/VM Guide for Automated Installation and Service. For more info, see APAR 64439 for z/VM 5.2 and z/VM 5.3 and informational APAR II14518 for z/VM 5.4 Xenia Tkatschow z/VM Performance Endicott, NY 13760 ---------------------------------------------------------------------- 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 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
<<attachment: BARTON.vcf>>
