Date: Sun, 7 Jan 2007 21:30:46 -0600 From: Dan Nelson <dnelson@allantgroup.com> To: David Gilbert <dgilbert@dclg.ca> Cc: freebsd-hackers@freebsd.org Subject: Re: dump reads more than restore writes? Message-ID: <20070108033046.GA41724@dan.emsphone.com> In-Reply-To: <17825.44456.556954.545497@canoe.dclg.ca> References: <17825.44456.556954.545497@canoe.dclg.ca>
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In the last episode (Jan 07), David Gilbert said: > I've got a command line like the following: > > dump -0af - /dev/ad1s1g | restore -rf - > > ... and I'm watching gstat. ad1s1g is not mounted. The disk on which > the restore is running is also quiet (nobody using the disk). > > And gstat says that ad1 is consistently reading 31 to 37 megabytes > per second and ad2 (the restore disk) is consistently writing 10 to > 13 megabytes per second. This is over hours --- the figures never > catch up. If you have a lot of small files, dump may be rereading directory information. Dump has a cache option that can help, but make sure you also dump a snapshot (i.e. always use -L when using -C). -- Dan Nelson dnelson@allantgroup.com
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