On Feb 10, 2007, at 9:33 PM, Christopher Browne wrote:
The fundamental trouble with this mechanism is that a power outage can
instantly turn a database into crud.

One may try to mitigate that problem by supporting the memory device
with multiple power supplies *and* multiple UPSes.

Ask me about the time a year ago that I had a 24x7 database, with two power supplies connected to two UPSes on independent mains circuits, dropped dead because one UPS was overloaded (more than one server connected to it, apparently too much) and the other UPS was simply dead (undetected zombie UPS), when a catastrophic power failure killed both of the generator backed mains circuits.

I wasn't pleased, but it happened nonetheless. A UPS is not a 100% guarantee of anything. They fail more often than they should. No amount of paranoia guarantees uptime.

That said, I see plenty of use for loosening restrictions on databases where the contents do not matter and a little loss is acceptable.


J. Andrew Rogers

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