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Re: A Very Bad umount

=?UTF-8?Q?=c3=89tienne_Mollier?= <etienne.mollier@mailoo.org> writes:
> Good Day Gene,
> Gene Heskett <gheskett@shentel.net> 2018-09-12T03:14 +0200 :

> Should a badly placed “rm” command occur on the system, the
> system and both of its backup disks would be wiped clean.  I
> don't believe the risk mentioned here over was related to disk
> decay.  It was more about minimizing the time frame when this
> catastrophe could happen.

	Precisely. I don't want to leave them mounted since we
might get a power hit that would corrupt the drives causing all
the backups to go poof!

	Bad stuff can even happen with good UPS's in line.

	When I was a systems engineer at Oklahoma State
University, we had a weird chain of events one cold and bright
Winter day just before Christmas in the mid nineties.

	A pigeon wandered in to a power sub station and pecked at
the wrong thing and received about 100-thousand volts through his
body, ruining his day for sure.  The power on the campus went
dark and our UPS's held until an auxiliary generator came on line
a few minutes later.  The problem was that it was running at the
wrong throttle setting, sending AC at near 50 HZ instead of 60 HZ
into our building.  The UPS's were older fero-resonant devices
and the frequency was far enough off that the UPS's stayed
switched to battery mode, something we were unaware of.

	About half an hour later, the batteries ran all the way
down and those computers connected to them suddenly lost power
without a proper shut-down.

	I think they came back okay but we were just lucky.

	Nothing sounds more odd than hearing all the electric
motors and fans in the building revving up and slowing down as
the generator throttle was adjusted to 60 HZ.

	The usb drives I am using for backups are SSD devices so
there are no moving parts.


> I wouldn't do both backups at the same time personally, If
> something very wrong occurs to the system at backup time, I'd
> still have the secondary backup available for restore.
> Things are a bit different when centralizing backup policies
> with tools like Amanda.
> > IMO the power savings from spinning down when not in active
> > use, do not compensate for the increased failure rate you'll
> > get under stop and start conditions.
> Interesting opinion, it could be worth verifying.  Keeping a
> machine running for BOINC, I only had a disk issue once since
> the beginning of the decade.  Building disks has energy costs
> too indeed.
> Kind Regards,
> --
> Étienne Mollier <etienne.mollier@mailoo.org>

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