Hi Geoff, The Canucks have already won their last game of the season :-) more below...
On Apr 18, 2010, at 11:21 PM, Geoff Nordli wrote: >> On Apr 13, 2010, at 5:22 AM, Tony MacDoodle wrote: >> >>> I was wondering if any data was lost while doing a snapshot on a >> running system? >> >> ZFS will not lose data during a snapshot. >> >>> Does it flush everything to disk or would some stuff be lost? >> >> Yes, all ZFS data will be committed to disk and then the snapshot >> is taken. >> > > Hi Richard. > > Can you explain in a little bit more detail how this process works? > > Let's say you are writing from a remote virtual machine via an iscsi target > set for async writes and I take a snapshot of that volume. > > Are you saying any outstanding writes for that volume will need to be > written to disk before the snapshot happens? Yes. > Setting the target to sync writes and using a ZIL might have better > performance, if you were doing a lot of snapshots. No. In this case we are referring to the sync(2) system call, which has nothing to do with how files are written. Unfortunately, the word "sync" is somewhat overloaded and frequently misapplied. > I know there is a potential to lose data with async set target, but the > virtual machines running on the system are just lab machines using > non-production data. There are use cases where this can be justified. > BTW, great Nexenta / ZFS class in Atlanta. Thanks for getting me on the > right track!! I'm glad you enjoyed it. I'm looking forward to Vegas next week and there are some seats still open. -- richard ZFS storage and performance consulting at http://www.RichardElling.com ZFS training on deduplication, NexentaStor, and NAS performance Las Vegas, April 29-30, 2010 http://nexenta-vegas.eventbrite.com _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
