Daniel Carosone <d...@geek.com.au> writes: >> you can fetch the "cr_txg" (cr for creation) for a >> snapshot using zdb, > > yes, but this is hardly an appropriate interface.
agreed. > zdb is also likely to cause disk activity because it looks at many > things other than the specific item in question. I'd expect meta-information like this to fit comfortably in RAM over extended amounts of time. haven't tried, though. >> but the very creation of a snapshot requires a new >> txg to note that fact in the pool. > > yes, which is exactly what we're trying to avoid, because it requires > disk activity to write. you missed my point: you can't compare the current txg to an old cr_txg directly, since the current txg value will be at least 1 higher, even if no changes have been made. >> if the snapshot is taken recursively, all snapshots will have the >> same cr_txg, but that requires the same configuration for all >> filesets. > > again, yes, but that's irrelevant - the important knowledge at this > moment is that the txg has not changed since last time, and that thus > there will be no benefit in taking further snapshots, regardless of > configuration. yes, that's what we're trying to establish, and it's easier when all snapshots are commited in the same txg. -- Kjetil T. Homme Redpill Linpro AS - Changing the game _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
