Bryan Tong Minh schrieb:
On Sat, Jan 17, 2009 at 10:30 AM, Daniel Kinzler
<daniel(a)brightbyte.de>
wrote:
Tripling space requirements seems a bit of
overkill. Maybe there's a
smarter solution. Ideas?
ZFS snapshots?
Hm, to quote the relevant section from wikipedia:
An advantage of copy-on-write is that when ZFS
writes new data, the
blocks containing the old data can be retained, allowing a snapshot
version of the file system to be maintained. ZFS snapshots are created
very quickly, since all the data composing the snapshot is already
stored; they are also space efficient, since any unchanged data is shared
among the file system and its snapshots.
Writeable snapshots ("clones") can also be created, resulting in two
independent file systems that share a set of blocks. As changes are made
to any of the clone file systems, new data blocks are created to reflect
those changes, but any unchanged blocks continue to be shared, no matter
how many clones exist.
So... this means we can have the two-backup-stages solution i suggested,
without wasting space, because the unchanged data is shared by between
tween the copies? That would be perfect!
-- daniel
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Actually it would be n-backup-stages. Snapshots need never be deleted. You
can have millions of them and they don't use up much space at all ...