On Sun, Oct 05, 2008 at 11:30:54PM -0500, Nicolas Williams wrote: > > 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
That would definitely be a great help. > 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. Maybe not, but it would at least save *something* as opposed to not saving anything at all. Still, with enough UPS power, there should be at least enough run time left to get the rest of the ZIL to the disk mirror. > 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. 4Gb FC is slow and low latency? Tell that to all my local fast disks that are attached via FC. :) > 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. Or would they? A box dedicated to being a RAM based slog is going to be faster than any SSD would be. Especially if you make the expensive jump to 8Gb FC. -brian -- "Coding in C is like sending a 3 year old to do groceries. You gotta tell them exactly what you want or you'll end up with a cupboard full of pop tarts and pancake mix." -- IRC User (http://www.bash.org/?841435) _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
