[Beowulf] Random numbers (was Re: /dev/random entropy on stateless/headless nodes)

David Mathog mathog at caltech.edu
Mon Feb 28 09:37:19 PST 2011

On _some_ systems one decent source of randomness, albeit at a low bit
rate, is lm_sensors. The machines I am referring to alternate randomly
between two different fan speed values or have varying low bits in their
temperature readings (at a constant workload, including idle).

If it is ok to go outside the node for this information, then rather
than mess about with transmission time delays the simplest thing would
be to run a pseudo random number generator on one node and have the
other nodes retrieve blocks of numbers from it.  If the server hands out
the generator output sequentially they will all receive different
blocks, and these can be stuffed into the ioctl to keep /dev/urandom happy.

Probably less work to keep the cluster behind a firewall and dispense
with applications (or application modes) that need /dev/urandom.


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

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