Power cut if temps are too high

bzs at theworld.com bzs at theworld.com
Wed May 29 04:27:39 UTC 2019

On May 28, 2019 at 19:56 owen at delong.com (Owen DeLong) wrote:
 > It’s unlikely to apply to much of anything in a datacenter other than disks.

Ok, disks, a mere bagatelle of a concern.

Then again obviously disks have gotten much, much better about thermal
change since people in, e.g., temperate climates might take their
laptops' running disks from a long, frigid walk into a warm building.

There was a time when you weren't supposed to move a disk while it was
still spinning (e.g., hot swaps had to be able to cut power before
removal so you could give the heads several seconds to stop and park),
not sure how they solved that so completely, again, laptops.

 > The reason it applies to disks is because rapid cooling of a drive will lead to uneven cooling of the platters which may cause abnormal stresses leading to shattering and/or warpage (depending on the material the drive platters are made from).

Also head clearances and other moving parts tolerances.

 > Most electronic components can tolerate a pretty steep thermal curve in either direction so long as the curve doesn’t take them out of spec one way or the other.
 > Also, most circuit boards and the like do not have enough mass to surface area ratio to lead to significant temperature differentials within a small physical distance.

Then again if you're cooling a room from, say, 115F to 70F you only
need one excuse to consider the rate of cooling and disks would be a
pretty good excuse.

SSDs no doubt are obsoleting even that concern.

But I still tend to worry about the relationship of resistance to
temperature in circuits as a general principle tho perhaps in the
likely range it's not a major concern.

Anyhow, IT'S WORTH A THOUGHT if something extreme happens to
temperatures in your machine room.

You might not want to fling open the doors and windows of a 110+F room
to 0F outside air and begin turning everything back on as the room's
air thermometer begins to register 70F a few minutes later.

Water condensation can also be a concern, after a prolonged A/C
failure it may be hot and humid in the room depending on the climate


 > Owen
 > > On May 28, 2019, at 12:18 , bzs at theworld.com wrote:
 > > 
 > > 
 > > Something to keep in mind is that some equipment, disks in particular,
 > > should only be cooled at a certain rate once they're hot, often
 > > annoyingly slow by the specs like 2-3 degrees C per hour but there are
 > > probably circuits sensitive to this also which could be anywhere.
 > > 
 > > It came up because it happened to me in Cambridge, MA in the dead of
 > > winter and every helpful person in the building came by to suggest I
 > > just open windows and doors to the snowy outdoors to get things
 > > running sooner.
 > > 
 > > It should be in the specs and if you're concerned about equipment
 > > running in too hot an environment you might be concerned about this
 > > also. Particularly after a forced power-down which also powers down
 > > equipment fans while the chips etc are still hot so will continue
 > > heating cases.
 > > 
 > > Ambient air temperature might not be telling you the whole story is
 > > the point.
 > > 
 > > I keep one of those big 5' fans, looks like something they use in
 > > Hollywood for windstorms and feels a bit like it on high, for just
 > > this sort of reason tho even if I just think it's getting warm, and
 > > several smaller fans to point at racks etc.
 > > 
 > > The best thing you can do if it gets too hot is keep the air moving.
 > > 
 > > (Where to plug the fans in after a power shutdown is your problem, I
 > > knew someone would think that!)
 > > 
 > > -- 
 > >        -Barry Shein
 > > 
 > > Software Tool & Die    | bzs at TheWorld.com             | http://www.TheWorld.com
 > > Purveyors to the Trade | Voice: +1 617-STD-WRLD       | 800-THE-WRLD
 > > The World: Since 1989  | A Public Information Utility | *oo*

        -Barry Shein

Software Tool & Die    | bzs at TheWorld.com             | http://www.TheWorld.com
Purveyors to the Trade | Voice: +1 617-STD-WRLD       | 800-THE-WRLD
The World: Since 1989  | A Public Information Utility | *oo*

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