> [google server with batteries] These are cool, and a clever rethink of the typical data centre power supply paradigm. They keep the server running, until either a generator is started or a graceful shutdown can be done.
Just to be clear, I'm talking about something much smaller, that provides power only for drives, for a few moments after the host powers down (for whatever reason) to let the drives sync their caches safely. Basically, just wrapping the drive with the supercap (or equivalent) the manufacturer didn't include, plus whatever minimal power supply circuitry is needed (to avoid big inrush recharge currents on startup, to avoid sending power back out into the rest of the case, etc). Because there's no integration for an emergency "sync now!" signal, we have to rely on timeouts and wait "long enough" for the cache to be sync'ed. It might be larger and need to hold longer than an on-board supercap, but not very long in absolute terms. There seems to be lots of room for a comfortable niche in the gap between common commodity hardware (that would be plenty good enough otherwise) and the $5k F20's and LogZilla's and similar. -- Dan.
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