Extra, the direct contact cooling stuff must still have the fans in the
nodes to keep the dimms/disks/power supplies cool... thus use considerably
more power than nodes without fans.
why do you say "considerably"? 1u muffin fans are annoying and not
that efficient, but even 1U could still use blowers. and it's not as if
you need a lot of airflow to keep 5-20W of support hardware cool.
(that would be for non-extreme numbers of disks/dimms/nics - though it
occurs to me that motherboards also have some power regulation in them,
and if 2 sockets are drawing 250w, then 90% efficient regulation would
still mean 28W extra heat to dissipate.)
iirc a typical 1U fan dissipates up to ~3W, but that's only when
running full on (screaming 14krpm...). not to mention the wide
availability of simple 4-system-in-2u chassis (more efficient fans).
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