filesystem snapshot question
jesse at wingnet.net
Sun Jan 18 20:11:56 PST 2004
I've read some of the documentation written about
the new filesystem snapshot feature in 5.x, and I've
used it a few times on my laptop. Very very slick.
However, I can't seem to find a good explanation of
exactly HOW it works and what performance issues are
involved. Snapshots don't seem to take up much disk
space. (even though `ls -al` will report that the
snapshot is as large as the slice on which it resides
at the time the snapshot was created)
So when a snapshot is active on a filesystem, does
every disk write happen twice? Once to the real
filesystem and once to the snapshot with old data?
I mean, it CAN'T actually be making a copy of the
filesystem. :) My disk doesn't have enough free space.
Is there a way to actually figure out how much data
the snapshot has allocated at any given time?
Does a snapshot physically grow on the disk as
changes are made to the real filesystem?
Just hoping to understand things better.
Jesse Guardiani, Systems Administrator
WingNET Internet Services,
P.O. Box 2605 // Cleveland, TN 37320-2605
423-559-LINK (v) 423-559-5145 (f)
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