On Apr 6, 2010, at 5:00 PM, Erik Trimble wrote: > On Tue, 2010-04-06 at 19:43 -0400, Kyle McDonald wrote: >> On 4/6/2010 3:41 PM, Erik Trimble wrote: >>> On Tue, 2010-04-06 at 08:26 -0700, Anil wrote: >>> >>>> Seems a nice sale on Newegg for SSD devices. Talk about choices. What's >>>> the latest recommendations for a log device? >>>> >>>> http://bit.ly/aL1dne >>>> >>> The Vertex LE models should do well as ZIL (though not as well as an >>> X25-E or a Zeus) for all non-enterprise users. >>> >>> The X25-M is still the best choice for a L2ARC device, but the Vertex >>> Turbo or Cosair Nova are good if you're on a budget. >>> >>> If you really want an SSD a boot drive, or just need something for >>> L2ARC, the various Intel X25-V models are cheap, if not a really great >>> performers. I'd recommend one of these if you want an SSD for rpool, or >>> if you need a large L2ARC for dedup (or similar) and can't afford >>> anything in the X25-M price range. You should also be OK with a Corsair >>> Reactor in this performance category. >>> >>> >> What about if you want to get one that you can use for both the rpool, >> and ZIL (for another data pool?) >> What if you want one for all 3 (rpool, ZIL, L2ARC)?? >> >> -Kyle >> > > It all boils down to performance and the tradeoffs you are willing to > make. For good ZIL, you want something that has a very high IOPS rating > (50,000+ if possible, 10,000+ minimum, particularly when writing small > chunks).
High write IOPS :-) > 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. > For rpool use, > you don't really care about performance so much, as it's almost > exclusively read-only Yep > (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. > 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 ZFS storage and performance consulting at http://www.RichardElling.com ZFS training on deduplication, NexentaStor, and NAS performance Las Vegas, April 29-30, 2010 http://nexenta-vegas.eventbrite.com _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
