From: T. Horsnell (tsh@mrc-lmb.cam.ac.uk)
Date: Mon Jan 16 2006 - 05:16:08 EST
Many thanks to all who replied.
Brad Bell hit the nail on the head.
I was trying to vrestore a 150Gbyte saveset containing many small files
(at least 2 million) to a UFS filesystem.
Since the default action on a UFS filesystem is to sync the metadata
to disk every time a file is closed, the write-rate slows drastically
when handling small files. iostat was sometimes reporting < 1Mbyte/sec
during small-file recovery, compared with 35-40Mbytes/sec when recovering
batches of big files.
There is a UFS mount option, '-o delayed', which prevents this per-file
syncing and which is documented in the man pages for mount (pity its not
mentioned in 'man vrestore') and which made a huge difference to my vrestore
speed. I got a tenfold increase in speed with this option applied
(reduced from 60 hours to 6.5).
Thanks again,
Terry.
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