May 15th, 2014

Seagate Kinetic and SMR

In the trivial things I never noticed department: Kinetic might have a technical merit. Due to the long history of vendors selling high-margin snake oil, I was somewhat sceptical of the object-addressed storage. However, they had a session with Joe Arnold of SwiftStack and a corporate person from Seagate (with an excessively complicated title), where they mentioned off-hand that actually all this "intelligent" stuff is supposed to help with SMR. As everyone probably know, shingle drives implement complicated read-modify-write cycles to support traditional sector-addressed model and the performance penalty is worse than 4K drive with 512-byte interface.

I cannot help thinking that it would be even better to find a more natural model to expose the characteristics of the drive to the host. Perhaps some kind of "log-structured-drive". I bet there are going to be all sorts of overheads in the drive's filesystem that negate the increase in the aerial density. After all, shingles only give you about 2x. The long-term performance of any object-addressed drive is also in doubt as the fragmentation mounts.

BTW, a Seagate guy swore to me that Kinetic is not patent-encumbered and that they really want other drive vendors to jump on the bandwagon.

UPDATE: Jeff Darcy brought up HGST on Twitter. The former-Hitachi guys (owned by WD now) do something entirely different: they allow apps, such as Swift object server, to run directly on the drive. It's cute, but does nothing to help the block-addressing API being unsifficient to manage a shingled drive. When software runs on the drive, it still has to talk to the rest of the drive somehow, and HGST did not add a different API to the kernel. All it does is kicking the can down the road and hoping a solution comes along.

UPDATE: Wow even Sage.