There’s been a lot of noise from the storage industry about flash recently - in particular, noise from EMC and Sun, both of whom recently announced storage products using flash, EMC in January and Sun earlier this month. Below are my thoughts on what EMC and Sun are doing, as well as what NetApp might do. Since I see a fair amount of visitors from all three companies here, if I’ve got something about your employer wrong, please correct me in the comments.
EMC’s approach seems to target the very high-end. I don’t have any EMC gear to play with, but if I understand correctly, their flash drives are pretty much plug and play with their DMX4 arrays, matching the physical form factor of their existing disk drives. Once the drives are in the array, you can do anything with them that you do with standard drives - these drives are just a lot faster. Sounds very much like a no-holds-barred-if-you-need-speed-this-is-how-we’ll-give-it-to-you - with a price to match the performance.
I’d love to have some of the EMC flash gear, but I doubt I’ll ever see this iteration. I work with NetApp storage arrays (at least for this budget cycle…), and from what I understand about the pricing of the EMC kit, it’s targeted way over the head of my employer. So will I see something similar from NetApp? Unfortunately, it doesn’t sound like they’ll have anything out in the near future. A couple years ago, Dave Hitz was almost dismissive of flash, answering “I don’t think so” and “I don’t care” to the question of whether flash would replace disk drives - and he has some good points, mainly that the storage and management layer is ultimately more important than the physical media one uses. More recently, Jay Kidd, NetApp’s chief marketing officer was quoted by ZDNet as saying that flash will become “an integral part” of enterprise storage - but there are no flash product announcements from NetApp that I’m aware of.
Given NetApp’s storage system architecture, this seems particularly unfortunate to me. SSDs seem like they could fit very nicely as a cache device between the controller and the conventional disk drives. I imagine that just a couple SSDs could give a substantial performance boost to an array for a very moderate price. Additionally, I don’t see a reason why NetApp couldn’t allow you to make an aggregate out of a shelf of flash drives for servers that need absolute top speed. Will they do either of these? I hope both, but we’ll have to wait and see.
(With their newly-announced Performance Acceleration Modules, NetApp seems to be acknowledging the value of an additional caching layer, although the PAM is for read performance only.)
Sun’s flash announcement is focused on the use of flash drives in their server hardware. Specifically, according to an Intel Developer Forum presentation, at least one use case Sun is targeting is ZFS, where direct-attached flash would be used in a cache role for specific ZFS reads and writes (in the second-level Adaptive Replacement Cache - L2ARC - and ZFS Intent Log - ZIL -pools - see page 11 of the above slides). The presentation suggests a possible configuration, comparing a hypothetical Sun X4450 with seven 10k RPM SAS drives and one with two SSDs and five 4200 RPM (did they mean 7200 RPM?) SATA drives. For almost the same price, the SSD/SATA system delivers substantially better Read IOPS and slightly better write IOPS.
Which is all good and nice - I do love a slide with reassuring bar graphs - but Sun won’t be shipping servers with flash drives until later this year. Additionally, the support for separating the L2ARC and ZIL is only in OpenSolaris, not Solaris - I haven’t seen word on when it will be backported. I also wonder about what effect single ZIL and L2ARC drives, as used in the scenario in the presentation, would have on a machine’s availability; Sun could presumably address this with some “best practices” documentation by the time they ship servers with SSDs. All that aside, I like what I see from Sun so far, particularly that they’ve found a use case for SSDs at a reasonable price point.
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