On Sun, Oct 05, 2008 at 09:07:31PM -0400, Brian Hechinger wrote: > On Sat, Oct 04, 2008 at 10:37:26PM -0700, Chris Greer wrote: > > I'm not sure I could survive a crash of both nodes, going to try and > > test some more. > > Ok, so taking my idea above, maybe a pair of 15K SAS disks in those > boxes so that you could create a backing store. I wonder what the best > way to setup realtime sync would be (without making the backing store > responsible for slowing down the ramdisk, so no zfs mirroring between > rmadisk and sas disk in other words).
There have been threads about adding a feature to support slow mirror devices that don't stay synced synchronously. At least IIRC. That would help. But then, if the pool is busy writing then your slow ZIL mirrors would generally be out of sync, thus being of no help in the even of a power failure given fast slog devices that don't survive power failure. Also, using remote devices for a ZIL may defeat the purpose of fast ZILs, even if the actual devices are fast, because what really matters here is latency, and the farther the device, the higher the latency. > > So is this idea completely crazy? > > I don't think so, no. ;) Yes, it's pretty smart. Add UPS and it's sortof like battery-backed RAM. You can probably get a good enough reliability rate out of this for your purposes, though actual slog devices would be better if you can afford them. Nico -- _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
