Bryan Tong Minh schrieb:
On Sat, Jan 17, 2009 at 10:30 AM, Daniel Kinzler daniel@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