dump reads more than restore writes?

Dan Nelson dnelson at allantgroup.com
Mon Jan 8 03:42:16 UTC 2007

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 at allantgroup.com

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