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esh-pfi-infrastructure/persistent-memory.d
vh dce261335e memory: run 3c goes to the GX10 — I priced the failure in the wrong units
The operator overruled my ana-ml2 recommendation and was right. I had step
times in hand, so I priced a breaker trip as eleven minutes of lost
training. That is the recompute cost and it is the cheapest component of
the loss.

A breaker trip at Anaheim is a forty-minute drive each way on the
operator's time, whenever he happens to notice, with thirteen hosts dark
until he arrives -- including the hypervisor most of them run on, the
fleet's primary backup server, and three SureFire client machines that are
a customer's production hosts under a hosting agreement.

So save_steps 100 to 50 caps the recompute, not the outage, and it was
never the mitigation I claimed. Thirteen hours unattended on a desk in NH3
beats two and a half hours that can put a client's hosts dark, especially
when nothing is waiting on this run.

Recorded the general form at length because it is the transferable part:
when recommending between options, check whether you priced the failure
mode in whatever units you happened to be measuring. A metric in hand will
volunteer itself as the unit of risk.

Also measured and dismissed the obvious third option: the RTX PRO 6000s
have a 250 W floor against a 300 W default, so capping both saves 100 W on
a box drawing about a kilowatt. Not enough to matter, and it costs
throughput to buy.
2026-09-02 01:17:49 -07:00
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