On Fri, Jan 14, 2005 at 10:49:44PM +0100, Anthony Atkielski wrote: > John writes: > > J> If you are running FreeBSD 5.x, you get the cool "L" option on > J> dump which will automatically snapshot the mounted filesystems. > > What exactly is meant by a "snapshot," and how much extra disk space > does it require when dump runs? I've seen the warnings when I run dump > on a running multiuser system in 5.x, and I turned on the L option, > since I'm not hurting on disk space, but I do wonder how much space it > requires (I can't imagine a snapshot that doesn't require a lot of disk > space).
Actually the snapshot requires practically no additional space: it's a
view of the filesystem at a particular point in time. Any subsequent
modifications -- new or edited or deleted files, etc. are held in
memory: they do take up a bit more space, but only until dump(8)
finishes running and all of the recent filesystem traffic can be
merged.
Cheers,
Matthew
--
Dr Matthew J Seaman MA, D.Phil. 8 Dane Court Manor
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