2012-08-01 23:40, opensolarisisdeadlongliveopensolaris пишет:
Agreed, ARC/L2ARC help in finding the DDT, but whenever you've got a snapshot destroy (happens every 15 minutes) you've got a lot of entries you need to write. Those are all scattered about the pool... Even if you can find them fast, it's still a bear.
No, these entries you need to update are scattered around your SSD (be it ARC or a hypothetical SSD-based copy of metadata which I also "campaigned" for some time ago). We agreed (or assumed) that with SSDs in place you can find the DDT entries to update relatively fast now. The values are changed in RAM and flushed to disk as part of an upcoming TXG commit, likely in a limited number of disk head strokes (lots to coalesce), and the way I see it - the updated copy remains in the ARC instead of the obsolete DDT entry, and can make it into L2ARC sometime in the future, as well. //Jim _______________________________________________ zfs-discuss mailing list email@example.com http://mail.opensolaris.org/mailman/listinfo/zfs-discuss