Wednesday, May 21, 2014

DAWN is breaking

I posted last October on Seagate's announcement of Kinetic, their object storage architecture for Ethernet-connected hard drives (and ultimately other forms of storage). This is a conservative approach to up-levelling the interface to storage media, providing an object storage architecture with a fixed but generally useful set of operations. In that way it is similar to, but less ambitious than, our proposed DAWN architecture.

The other half of the disk drive industry has now responded with a much more radical approach. Western Digital's HGST unit has announced Ethernet connected drives that run Linux. This approach has some significant advantages:
  • It sounds great as a marketing pitch.
  • It gets computing as close as possible to the data, which is the architecturally correct direction to be moving. This is something that DAWN does but Kinetic doesn't.
  • It will be easy to make HGST's drives compatible with Seagate's by running an implementation of the Kinetic protocol on them.
  • It provides a great deal of scope for researching and developing suitable protocols for communicating with storage media over IP.
But it is also very risky:
  • In many cases manufacturers find disks returned under warranty work fine; the cause of the failure was an unrepeatable bug in the disk firmware. Running Linux on the drive will provide a vastly increased scope for such failures, and make diagnosing them much harder for the manufacturer.
  • If the interface between the Linux and the drive hardware emulates the existing SATA or other interface, the benefits of the architecture will be limited to some extent. On the other hand, to the extent it exposes more of the hardware it will increase the risk that applications will screw up the hardware.
  • Kinetic's approach takes security of the communication with the drives seriously. HGST's "anything goes" approach leaves this up to the application.
On balance I think that HGST's acceptance that up-levelling the interface to media is important is a very positive development.

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