Your experience is really informative. Thanks for giving me such a
really precious information. Since I am a researcher, I rarely faces
on real troubles.

Andrew, I agree with you. UPS is not reliable all the time.
On the other hand, however, disks or raids are also not reliable all the time.
Moreover, on the earth, there is NO device which completely assures
durability of the ACID transaction property. Even if disks and power
supplies are perfect, the system would be destroyed by an earthquake
(thus, disaster recovery techniques are recently popular). Thus I
think the problem is not in a device. It is in the management of
system administrators. (However, this is just my opinion and it is not
objective one required by large questionnaire).

On the other hand, speed is required. My first motivation of this work
is a friend of mine who is working at a financial firm. He strongly
required performance of UPDATE/INSERT on the database servers in his
company (the database was a major commercial product). I think in such
a rich environment, strong power management facilities may be expected
though this is just my one thought).

In summary, I think the problem lies in system management rather than
device itself.


-- Hideyuki

J. Andrew Rogers wrote:

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 

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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