Not that I want to bring this subject back up, but I think there were a few unanswered questions.
You can find the device queueing on Performance Toolkit FCX108 DEVICE report under the "Req. Qued" field. Also is reflected in difference between "Serv" & "Resp" (Service Time and Response Time). Shown in example below where MDC is not enabled. <-- Device Descr. --> Mdisk Pa- <-Rate/s-> <------- Time (msec) -------> Req. Addr Type Label/ID Links ths I/O Avoid Pend Disc Conn Serv Resp CUWt Qued >> All DASD << .... .5 .0 .2 .1 2.0 2.3 2.3 .0 .00 80C9 3390-3 US7E42 158 4 358 .0 .2 .0 2.0 2.2 6.0 .0 1.37 For those still running VMPRF, it would be on the DASD_BY_ACTIVITY Report. In regards to paging to 3390-9s, yes, it would be a horrible idea if it were a real 3390-9. Otherwise, it can be done depending on the rest of the configuration. I would avoid it, if I could. But if you are approaching the max of 256 CP owned volumes: 1) I'd like to hear from you. 2) Your access density for paging is probably low enough that it doesn't matter at this point. For those wanting to read more about Linux and PAV on VM see: http://awlinux1.alphaworks.ibm.com/developerworks/linux390/perf/tuning_rec_dasd_PAV.shtml#begin In regards, to the skew of access density. Traditionally, minidisk cache addresses that and is why it was designed the way it was versus a private cache structure. But I don't agree that it is queuing on the device level that is the bulk of the I/O performance problems. The last 5 I/O problems I looked at were: 1 - channel contention on ESCON channels 2 - not balancing I/O across ranks 3 - not using minidisk cache 4 - PPRC config related 5 - application boo boo For those looking to blame someone for the lack of z/VM PAV support for minidisks and CP volumes, feel free to blame me; but be nice, my Mom & my manager might be reading this. For those that want to discuss their systems and choices, feel free to contact me. I'll respond as time permits. :-) Bill Bitner - VM Performance Evaluation - IBM Endicott - 607-429-3286 ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390
