> From: zfs-discuss-boun...@opensolaris.org [mailto:zfs-discuss- > boun...@opensolaris.org] On Behalf Of Hernan F > > Hi, > Out of pure curiosity, I was wondering, what would happen if one tries > to use a regular 7200RPM (or 10K) drive as slog or L2ARC (or both)?
I tested it once, for the same reasons as you. Curiosity. I never said anything about it because it wasn't interesting. In some cases, it accelerates some. In some cases, it slows things down. It basically depends on the characteristics of your work load, but overall, it was a net zero gain. Or perhaps a net loss. Generally speaking, people won't sacrifice the hardware or disk slots, unless there's a clear gain. So that's the conclusion. Obvious though it may be. There is no clear gain, so just don't do it. Offhand, I think the only situation where there was a gain was ... If the primary pool (6 disks) is being absolutely hammered by async operations, and then you benchmark some sync writes simultaneously, with and without the extra disk for dedicated log. The end result is: Since the dedicated log is idle, the sync write can immediately write to it, and then become just another async write going along with the crowd. Without the dedicated log, the sync write competes against the async operations for access to the main pool, slowing itself down and the async operations. But with the dedicated log, you've got 6 disks active with async operations and the 7th disk is idle during normal async operations ... But when you mix the async and sync operations, then suddenly you're able to leverage all 7 disks and have a net gain because your primary pool is not dorking around with tiny little sync operations. Like I said. Unimpressive, not interesting. No general purpose, and generally no gain. Don't do it. Just by the SSD instead. _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
