Ivan Voras wrote:
Scott Long wrote:
An alternate SoC project that would be very useful is block-level
snapshots. I'm not sure if I'll be able to retain the filesystem
snapshot functionality in UFS with journalling enabled, so moving to
doing the snapshots in the block layer would be a good way to make up
for this. Beware that while the GEOM transform would be pretty
One addenum that was introduced after I made the post to hackers@, but
before sending a proposal to Google (PHK's idea, actually) is to
implement a delayed-commit mode, in which journaled data will not be
commited until requested.
This would allow something like block-level snapshots, but one-shot only
(or at least one per journal).
Again, I'm not exactly sure how a generic mechanism can handle the
distinction of data vs. metadata vs. journal data. Also, what you
need to delay is not the journal writes, but the metdata writes.
In order for journal replay to work, the on-disk journal must
always be ahead of the on-disk metadata, and the proper bookkeeping
must be kept to track what sectors have been committed to the drive
and what sectors haven't. Again, you simply don't get this 'for free'.
Scott
_______________________________________________
freebsd-hackers@freebsd.org mailing list
http://lists.freebsd.org/mailman/listinfo/freebsd-hackers
To unsubscribe, send any mail to "[EMAIL PROTECTED]"
