> From: opensolaris-discuss-boun...@opensolaris.org [mailto:opensolaris- > discuss-boun...@opensolaris.org] On Behalf Of Justin Skariah > > I have a doubt regarding zfs snapshots. When I take a zfs snapshot does it > commit to the disk after logging in ZIL or it remains in ZIL till a DMU > transaction group commit happens.
At all times, there exists in RAM, a data structure that represents the present state of the filesystem. As processes send writes to the filesystem, those writes occur in RAM, and according to schedule, they get committed to disk as a TXG. If a process writes in SYNC mode, then the process cannot continue until after the write is committed to nonvolatile storage. So ZFS immediately records this intent in the ZIL, and then the SYNC mode write can exist in RAM, waiting for a TXG just like all the other ASYNC mode writes. Meanwhile the process has been freed up to continue processing. When you make a snapshot, the parent node of the filesystem is copied and preserved. It's an instant operation. I don' t know if this is instantly committed to disk, or if it's allowed to be buffered and written in the next TXG. Your question didn't really make any sense, so hopefully I've answered it. _______________________________________________ opensolaris-discuss mailing list opensolaris-discuss@opensolaris.org
