[snip]
Generally speaking, if you have a large cluster, and you have enough
work for it, it is going to be running flat out 24x7. If it isn't,
you've bought more hardware than you need.
There are many cases where a cluster is not used for continuously for
calculations, but rather to reduce turn-around. Our cluster for instance
is sitting idle at least 1/2 the time, but keeping it's size to the
point where when people do run they can get their results back in 8
hours or less makes them much more productive. This way they can look at
the results, tweak things as necessary, and run again while the setup is
still fresh in their mind.
Again, though, I think you might want to ask if you're doing the right
thing here. If all your machines are not working flat out 100% of the
time, you have hardware depreciating (and rapidly becoming obsolete)
to no purpose, and there are loads of people out there, probably even
on your own campus, who probably are desperate for compute
cycles. (Hell, I could use extra cycles -- I can never afford enough.)
We've been trying to encourage other departments on campus to use some
of our extra cluster time, but with rather mixed results.
Optimally, a cluster will be working 100% of the time, until one day
when it is obsolete (that is, the cost in space, power, and cooling
is more than replacing it with faster/better hardware), it gets shut
down, replaced, and sold off.
Perry
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