Re: fsck on boot...revisited
On Fri, 2013-07-26 at 19:01 +0100, Dom wrote:
> On 26/07/13 17:53, Ralf Mardorf wrote:
> > On Fri, 2013-07-26 at 11:54 -0400, Stefan Monnier wrote:
> >>> The system in question is running from an SSD, which I assume changes your
> >>> assumptions quite a bit. With a traditional HDDs, the loss of power
> >>> causes a head crash, etc which does in turn lessen the life of the drive.
> >>
> >> Actually, I fail to see why a power outage would have any negative
> >> effect on an HDD (e.g. why would the "head crash"?).
> >
> > In the old days the heads were not driven back, but for around more than
> > 20 years the heads will park by the momentum of the turns, when there
> > should be a blackout. IIRC if the drives didn't turn fast enough, the
> > heads could crash. Today a power outage definitively doesn't cause a
> > crash and AFAIR even my old 42 MB SCSI survived power outages.
>
> True. Back in those days the heads on some disks had to be sent a "park"
> command before powering off and what that did was to move the head to an
> reserved area of the disk before landing. Modern drives park the heads
> off the disks completely.
>
> I do remember so old 500MB mainframe disk units (14 inch 10 platter or
> so, 4 per unit) that had a slight fault. The normal procedure was to
> press the "offline" button, which retracted the heads from the disk,
> then press the "power" button to turn them off. Due to a glitch in the
> circuitry this would sometimes result in a surge in the head actuator
> coil and the heads would move back across the disks just as they stopped
> spinning, resulting in major damage to the entire unit. Later a small
> button was fitted which disconnected the coil and we had to hold that
> down until the disk had stopped spinning.
JFTR in the meantime I read the German Wiki and it claims that heads
automatically are parked since 1989, IOW >= 24 years ago there was this
issue. http://de.wikipedia.org/wiki/Head-Crash
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