Tristram Scott <tristram.sc...@quantmodels.co.uk> wrote:
> I see a number of points to consider when choosing amongst the various
> suggestions for backing up zfs file systems. In no particular order, I have
> these:
Let me fill this out for star ;-)
> 1. Does it work in place, or need an intermediate copy on disk?
Yes
> 2. Does it respect ACLs?
not yet (because of missing interest from Sun)
If people show interest, a ZFS ACL implementation would not take much time
as there is already UFS ACL support in star.
> 3. Does it respect zfs snapshots?
Yes
Star recommends to run incrementals on snapshots. Star incrementals
will work correclty if the snapshot just creates a new filesystem ID but
leaves inode numbers identical (this is how it works with UFS snapshots).
> 4. Does it allow random access to files, or only full file system restore?
Yes
> 5. Can it (mostly) survive partial data corruption?
Yes for data curruption in the archive, for data currupion in ZFS -> see ZFS
> 6. Can it handle file systems larger than a single tape?
Yes
> 7. Can it stream to multiple tapes in parallel?
There is Hardware for this task (check for "TAPE RAID")
> 8. Does it understand the concept of incremental backups?
Yes
And regarding the speed for incrementals:
A scan on a Sunfire X 4540 with a typical mix of small and large files (1.5 TB
of filesystem data in 7.7 million files) takes 20 minutes. There seems to be a
performance problem in the ZFS implementation: The data is made from 4 copies
of identical file sets, each 370 GB in size and the performance degrades after
some time. During parsing the first set of files, the performance is 4x higher,
so this 1.5 TB test could have been finished in 5 minutes.....
This test was done with an empty cache. With a populated cache, the incremental
scan is much faster and takes only 4 minutes.
It seems that incrementals at user space level still are feasible.
Jörg
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joerg.schill...@fokus.fraunhofer.de (work) Blog:
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