On Mon, 21 May 2007 11:26:20 -0700, Lionel B. Dyck <[EMAIL PROTECTED]> wrote:
>Thanks - you're points on YMMV is very appropo - I was just looking for >starting points. > >Lionel B. Dyck, Consultant/Specialist >Enterprise Platform Services, Mainframe Engineering >KP-IT Enterprise Engineering, Client and Platform Engineering Services >(CAPES) >925-926-5332 (8-473-5332) | E-Mail: [EMAIL PROTECTED] >AIM: lbdyck | Yahoo IM: lbdyck >Kaiser Service Credo: "Our cause is health. Our passion is service. We?r e >here to make lives better.? I think rules of thumb are a bad starting point. They either give you false sense of security, or you waste time trying to track down non- existent problems. We have run VM systems at 100% CPU utilization without problems -- but it was because we had enough low-priority work to sop up the cycles. With a "lumpier" workload (such as Linux guests), you might get in trouble somewhere between 80-100%. The 60% that someone cited seems extreme, but if you need to hold cycles in reserve, then you do. I/O and paging rates sustainable depend largely on the capability of the I/O subsystem. But long before you approach that capacity, you will start seeing problems due to queuing on a device. Adding more paging device addresses may help, for example. Some queuing is hidden though -- it exists but you will never see it. Clearly, you cannot run at above 100% of the CPU capacity or the I/O capacity. But it is very workload dependent on how close you can get to 100%.
