Our e-mail server started to slow down today. One of the disk devices
is frequently at 100% usage. The heavy writes seem to cause reads to
run quite slowly. In the statistics below, `c0t0d0' is UFS, containing
the / and /var slices. `c0t1d0' is ZFS, containing /var/log/syslog,
a couple of databases, and the GNU mailman files. It's this latter
disk that's been hitting 100% usage.
$ iostat -xn 5 3
extended device statistics
r/s w/s kr/s kw/s wait actv wsvc_t asvc_t %w %b device
8.2 57.8 142.6 538.2 0.0 1.7 0.1 25.2 0 48 c0t0d0
5.8 273.0 303.4 24115.9 0.0 18.6 0.0 66.7 0 73 c0t1d0
extended device statistics
r/s w/s kr/s kw/s wait actv wsvc_t asvc_t %w %b device
0.0 57.2 0.0 294.6 0.0 1.3 0.0 22.1 0 64 c0t0d0
0.2 370.2 1.1 33968.5 0.0 31.4 0.0 84.9 1 100 c0t1d0
extended device statistics
r/s w/s kr/s kw/s wait actv wsvc_t asvc_t %w %b device
0.8 61.0 6.4 503.0 0.0 2.5 0.0 40.0 0 70 c0t0d0
0.0 295.8 0.0 35273.3 0.0 35.0 0.0 118.3 0 100 c0t1d0
This system is running Solaris 10 5/09 on a Sun 4450 server. Both the
disk devices are actually hardware-mirrored pairs of SAS disks, with
the Adaptec RAID controller. Can anything be done to either reduce
the amount of I/O or to improve the write bandwidth? I assume that
adding another disk device to the zpool will double the bandwidth.
/var/log/syslog is quite large, reaching about 600 megabytes before
it's rotated. This takes place each night, with compression bringing
it down to about 70 megabytes. The server handles about 500,000
messages a day.
--
-Gary Mills- -Unix Group- -Computer and Network Services-
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