Thanks to everyone who responded, but to summarise, verbatim from Deborah Santomauro's email. Do an "iostat -xn 30" (display output in tabular format for 30 second refresh). Look at "%b" column - this is the percentage of time that the disk is busy. If this column is over 20 for any disk, then that disk may be a potential problem. Next look at the "asvc_t" column - this is the average service time for active transactions in milliseconds. Typically any disk that has a "%b" greater than 20 and an "asvc_t" exceeding 50 milliseconds, then that system is essentially bound by that disk - i.e. bottleneck problem that is rather severe. Another column to look at is "%w". This is the percentage of time there are transactions waiting for service. Normally this number should be below "5" for each disk. Higher than that, it could be an indication that the SCSI bus may be overloaded. Ideal situation is when it's at "0". With "sar" the queue lengths and wait times are measured when there is something in the queue. If "%busy" is small, large queues and service times probably represent the periodic efforts by the system to ensure that altered blocks are written to the disk in a timely fashion. My original question : I run a sar -d and get the following output which shows avserv sitting around 50.5 all day. Could anyone explain what if any performance hit the box may be taking. The sd0,h is the primary swap. The is a rather heavily used 5500. Is it worthwhile addressing this or is the performance gain minimal ? SunOS incldk01 5.6 Generic_105181-26 sun4u 02/19/02 08:00:01 device %busy avque r+w/s blks/s avwait avserv 08:20:01 sd0 7 1.0 11 146 36.2 50.5 sd0,h 7 1.0 11 146 36.2 50.5 08:40:01 sd0 6 1.0 11 134 37.5 52.4 ...... ..... Nigel.R.Owen Unix Support Enterprise Networks & eBusiness Midrange System Support Donnybrook House 01-6413492 This document is strictly confidential and is intended for use by the addressee unless otherwise indicated. Allied Irish Banks This Disclaimer has been generated by CMDis _______________________________________________ sunmanagers mailing list sunmanagers@sunmanagers.org http://www.sunmanagers.org/mailman/listinfo/sunmanagersReceived on Tue Feb 26 10:02:03 2002
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