Date: Mon, 5 Mar 2001 16:31:45 -0800 (PST) From: Matt Dillon <dillon@earth.backplane.com> To: Dan Phoenix <dphoenix@bravenet.com> Cc: freebsd-hackers@FreeBSD.ORG Subject: Re: systat -vmstat or iostat IO help Message-ID: <200103060031.f260VjC47207@earth.backplane.com> References: <Pine.BSO.4.21.0103051422030.6833-100000@gandalf.bravenet.com>
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:systat -vmstat
:
:Disks ad0 acd0 fd0 md0 89 ofod intrn
:KB/t 4.35 0.00 0.00 0.00 85 %slo-z 61952 buf
:tps 13 0 0 0 104 tfree 42 dirtybuf
:MB/s 0.05 0.00 0.00 0.00 36095 desiredvnodes
:% busy 100 0 0 0 58692 numvnodes
:
:well vmstat showing 100% busy and iostat showing 10% busy......
:IO an issue here or not?
:...
:Dan
systat -vmstat is correct. I usually use 'systat -vm 1'. If you see
100% busy for more then a few seconds then the disk is saturated
(almost certainly seek-limited). Solutions depend on what the system
is doing. Mail systems are the least scaleable, requiring you to
add additional disks for spools or a stripe, or additional machines
and use an MX round robin. Most other services can be scaled well
simply by adding memory or cpu. SCSI disks usually do better then IDE
in seek-limited situations. Higher-RPM disks can make a big difference
too.
-Matt
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