On Mon, May 09, 2005 at 05:07:10AM +1000, Tim Starling wrote:
Putting half your hardware on one grid and half on another means you
lose half your capacity if the power goes off. There is no need for
this. There is already a diesel generator on site, we just need to cover
various kinds of short-term failure. We've seen two short-term failures:
a main circuit breaker trip and a power strip circuit breaker trip. The
power strip failure could have been prevented by having a proper PDU
with independent breakers, I believe one is now on order. Various
threats to the main power, including the main circuit breaker, can be
dealt with by supplying the DB servers with a UPS, and negotiating with
the colo to ensure that their supply is fully redundant. The main power
failure apparently only lasted for a matter of seconds, if they don't
intend to guard against such short failures, then we need to make our
own arrangements.
Mention of PDUs reminds me of something: In conversation with one of the
people at the colo on Friday, I was informed that once the move is
accomplished (some of you should already know what I'm talking about,
and it's to them I speak) we'll be using circuits with lower amperage,
but will have more circuits per rack. Instead of 33 amp circuits (or
was it 30?), we'll be using 20 amp circuits -- and I think he said we'll
have three circuits per rack. This gives better power redundancy so
that less machines are affected by a failure on a single circuit and
less daisy-chaining of PDUs goes on (of course, we're talking about
fixing that daisy-chain thing anyway, at this point).
With that in mind, I don't know (since I'm not really in the loop on the
hardware-ordering side of things) whether that affects the ideal
situation for ordering PDUs. I know that we're interested in having all
network administrated PDUs so that we can use them for restarting
machines remotely, and I know we were looking at those "zero U" PDUs
that would basically fit two per rack. Should we be looking into
different PDUs if we'll have three circuits per rack, or should we just
get two of the zero U PDUs and get a couple of in-rack PDUs to hook up
to the third circuit?
Something to think about, I guess.
--
Chad Perrin
[ CCD CopyWrite |
http://ccd.apotheon.org ]