Strange magtape anecdote
paulkoning at comcast.net
Tue Oct 27 11:33:29 CDT 2020
> On Oct 27, 2020, at 11:08 AM, Dave Wade G4UGM via cctalk <cctalk at classiccmp.org> wrote:
> I remember when doing standby power generator tests we had to remember to off-line all the drives at end of job, other wise they all tried to rewind at the same time....
> .. and the generator could comfortably do two, stuttered a bit with three, but on the first test as the fourth flicked in there was a big "bang" and lots of flapping of tape, plus lots of cursing from our Site Engineer.,,,,
A similar issue shows up with large collections of disk drives. That includes modern small HDDs. The motor start surge current is a lot higher than the steady state current, so starting a row of drives all at once -- or a box full of 3.5 inch HDDs in a modern storage array -- can cause an overload.
In storage array firmware that's dealt with by spinning up the drives a couple at a time, fewer at a time if one of the power supplies has failed.
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