Racks vs. pile of PCs

[David Mathog]

Marshall E. Fryman mfryman at futuraintl.com said:

|>5.  Maintenance costs (rack parts tend to be nonstandard
|>     and expensive to replace, for instance, 1U power supplies).

|How often do you have to change them? Any good power supply should have
a 
|MTBF of 50k hours or so. That's about 5.7 years. Even a a 20k is still
2.2 
|years.

5.7years/unit.  If you have 20 units -> 5.7*12/20 = 3.4 months between
failures.  But that's only for the random sort of hardware/electrical
failure.
Normally what happens is you buy N of them, run them continuously,
and the fans start failing one after another at 3 years (or whenever)
because they all burn out their bearings after a roughly equivalent
amount
of service time.

|8.9% difference in price
You spec'd an expensive motherboard with dual processors for $940,
going with a single processor motherboard that same cost  would have
been
about $340.  Subtracting the $600 difference gives $983 vs $853
which is a 15% price increase for pile->rack.  Then you have to figure
in about $1000 for the rack, which brings it pretty close to 20%
difference.
Of course, that's build it yourself prices pile vs. rack.  Buy it from a
company
and the rack shoots way up in price (as would the PC style systems.)

Regards,.

David Mathog
mathog at caltech.edu
Manager, Sequence Analysis Facility, Biology Division, Caltech