> From: zfs-discuss-boun...@opensolaris.org [mailto:zfs-discuss- > boun...@opensolaris.org] On Behalf Of Tiernan OToole > > This might be a stupid question, but here goes... Would adding, say, 4 4 or > 8gb usb keys as a zil make enough of a difference for writes on an iscsi shared > vol? > > I am finding reads are not too bad (40is mb/s over gige on 2 500gb drives > stripped) but writes top out at about 10 and drop a lot lower... If I where to > add a couple usb keys for zil, would it make a difference?
Unfortunately, usb keys, even the fastest ones, are slower than physical hard drives. I even went out of my way to buy a super expensive super fast USB3 16G fob... And it's still slower than a super-cheap USB2 sata hard drive. There is a way you can evaluate the effect of adding a fast slog device without buying one. (It would have to be a fast device, certainly no USB fobs.) Just temporarily disable your ZIL. That's the fastest you can possibly go. If it makes a big difference, then getting a fast slog device will help you approach that theoretical limit. If it doesn't make a huge difference, then adding slog will not do you any good. To disable ZIL, if your pool is sufficiently recent, use the zfs set sync= command. It takes effect immediately. If you have an older system, you'll have to use a different command, and you'll probably have to remount your filesystem in order for the change to take effect. _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
