On Fri, Mar 4, 2011 at 11:58 AM, John Hanley <[email protected]> wrote:
> We will soon be installing a XIV storage system and connecting it to our > z10's. > Each z10 is running multiple VM 6.1 LPARS and will use the XIV for Linux > guests. > I would like to use EDEV's to allocate multiple FBA packs to be used as > needed > by the Linux guests, like I do now with ECKD full pack mdisks. > My worry is that I have read of significant path length increase in the > hypervisor with > EDEVICE I/O resulting in increased CPU usage. > Anyone notice this? It's one my list for sure. And has been for a while because it depends a lot on the workload. There were a few surprises in my initial measurements that got me off-track. Focus more on ECKD and native FCP because that is more common. You probably looked at this already: http://www.vm.ibm.com/perf/reports/zvm/html/520lxd.html What's missing there is how each customer weighs the other advantages of each option (like easier D/R, backups and security). When you read anything about performance of emulated FBA on FCP, do validate the z/VM release it applies to. The first release that introduced emulated FBA was a quick and dirty approach to reuse some existing code. The result was a bit disappointing. Subsequent z/VM releases improved a lot and some customers left the party early. >From a system administration point of view, EDEV is superior to both ECKD and native FCP. It would probably be good to understand which workload can take advantage of that. As long as your application is not I/O constrained, the extra cost of doing I/O may be acceptable. Servers with low utilization may be able to take advantage of MDC better and avoid I/O. What kind of workloads would you be looking at? Rob -- Rob van der Heij Velocity Software http://www.velocitysoftware.com/
