snapshot implementation
Bob Friesenhahn
bfriesen at simple.dallas.tx.us
Wed Dec 23 16:41:36 UTC 2009
On Wed, 23 Dec 2009, Patrick Proniewski wrote:
> By the way, I'm also interested in ZFS: is the snapshot technology
> available in ZFS the same as the one available in UFS?
I don't know anything about snapshots in UFS, but snapshots in ZFS are
certainly remarkably different. ZFS uses copy-on-write (COW) whenever
a data block is updated and snapshot creation simply adds a new
reference to existing blocks. The snapshot is made available as a
(usually) hidden directory (/filesystem/.zfs/snapshot/snapname) which
contains the complete filesystem content at the time the snapshot was
taken. In my experience, ZFS snapshots usually take less than a
second to complete. They are so efficient that some systems have
snapshots scheduled to be taken every five minutes as a defense
against user/application error.
Bob
--
Bob Friesenhahn
bfriesen at simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer, http://www.GraphicsMagick.org/
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