Date: Wed, 31 May 2006 08:05:21 -0700 From: "Eugene M. Kim" <freebsd.org@ab.ote.we.lv> To: freebsd-hackers@freebsd.org Subject: dump(8) performance Message-ID: <447DB0B1.8040206@ab.ote.we.lv>
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While watching the output of iostat -dxz -w10 -n100 to monitor the progress/performance of a dump(8) process straight to a tape, I found out something interesting and disappointing at the same time: The disk read throughput was exactly twice as high as the tape write throughput, throughout the entire dump phases 4 and 5, i.e. dumping actual inodes. Disappointing, because the tape drive utilization (%busy) was lingering around 35%-50% for most of the time; I didn't expect the disk would be the bottleneck. :p I want to believe that this indicates a bug in dump(8) which causes each disk block to be read twice, but being no UFS expert in any sense, I wonder: Could this behavior be by design, and would there be any room for improvement? Puzzled, Eugene
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