Date: Fri, 09 Jan 2009 09:50:27 -0700 (MST) From: "M. Warner Losh" <imp@bsdimp.com> To: hackers@freebsd.org Subject: 3x read to write ratio on dump/restore Message-ID: <20090109.095027.-1672857892.imp@bsdimp.com>
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I just copied a disk using dump + restore. I noticed something
through the whole run of this 500GB operation:
L(q) ops/s r/s kBps ms/r w/s kBps ms/w %busy Name
3 231 231 14754 9.5 0 0 0.0 97.5| da1s1a
0 39 0 0 0.0 39 4982 10.0 38.7| da2s1a
The read kBps was 3x the write kBps. While the dump is going through
the raw device, and the restore is going through the file system, I
can't imagine why we'd have such a huge difference that would be utter
consistent for the whole 15 hour run.
Any ideas what gives? I observed this with 16MB cache and with 32MB
cache, fwiw.
Warner
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