On Tue, 2010-04-06 at 17:17 -0700, Richard Elling wrote: > On Apr 6, 2010, at 5:00 PM, Erik Trimble wrote:
[snip] > > For L2ARC, you are more concerned with total size/capacity, and > > modest IOPS (3000-10000 IOPS, or the ability to write at least 100Mb/s > > at 4-8k write sizes, plus as high as possible read I/O). > > The L2ARC fill rate is throttled to 16 MB/sec at boot and 8 MB/sec later. > Many SSDs work well as L2ARC cache devices. > Where is that limit set? That's completely new to me. :-( In any case, L2ARC devices should probably have at least reasonable write performance for small sizes, given the propensity to put things like the DDT and other table structures/metadata into it, all of which is small write chunks. I tried one of the old JMicron-based 1st-gen SSDs as an L2ARC, and it wasn't much of a success. Fast read speed is good for an L2ARC, but that's not generally a problem with even the cheap SSDs these days. > > (one should generally not configure a swap device > > on an SSD-based rpool). > > Disagree. Swap is a perfectly fine workload for SSDs. Under ZFS, > even more so. I'd really like to squash this rumour and thought we > were making progress on that front :-( Today, there are millions or > thousands of systems with deployed SSDs as boot and swap on a > wide variety of OSes. Go for it. Really? I'm generally not good for running swap on lower-performing SSDs over here in Java-land, but that may have to do with my specific workload. I'll take your word for it (of course, I'm voting for swap not being necessary on many machines these days). > > You could probably live with an X25-M as something to use for all three, > > but of course you're making tradeoffs all over the place. > > That would be better than almost any HDD on the planet because > the HDD tradeoffs result in much worse performance. > -- richard > True. Viva la SSD! -- Erik Trimble Java System Support Mailstop: usca22-123 Phone: x17195 Santa Clara, CA Timezone: US/Pacific (GMT-0800) _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
