Re: [gentoo-user] How can I power disk off?

[Michael Mol <mikemol@gmail.com>]

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On Oct 6, 2011 9:06 PM, "Mark Knecht" <markknecht@gmail.com> wrote:
>
> On Thu, Oct 6, 2011 at 1:28 PM, Michael Mol <mikemol@gmail.com> wrote:
> > On Thu, Oct 6, 2011 at 4:21 PM, Mark Knecht <markknecht@gmail.com>
wrote:
> >> On Thu, Oct 6, 2011 at 1:03 PM, Paul Hartman
> >> My worry was that if the mdraid daemon saw one drive gone - either
> >> when starting to spin down or when one spins up slowly - and if mdraid
> >> didn't understand that all this stuff was taking place intentionally
> >> then it might mark that drive as having failed.
> >
> > Does mdraid even have an awareness of timeouts, or does it leave that
> > to lower drivers? I think the latter condition is more likely.
> >
> > I suspect, though, that if your disk fails to spin up reasonably
> > quickly, it's already failed.
> >
>
> In general I agree. However drives that are designed for RAID have a
> feature known as Time Limited Error Recovery (TLER) which supposedly
> guarantees that they'll get the drive back to responding fast enough
> to not have it marked as failed in the RAID array:
>
> http://en.wikipedia.org/wiki/Time-Limited_Error_Recovery
>
> When I built my first RAID I bought some WD 1TB green drives, built
> the RAID and immediately had drives failing because they didn't have
> this sort of feature. I replaced them with RAID Edition drives that
> have the TLER feature and have never had a problem since. (Well, I
> actually bought all new drives and kept the six 1TB drives which I'd
> mostly used up for other things like external eSATA backup drives,
> etc...)
>
> Anyway, I'm possibly over sensitized to this sort of timing problem
> specifically in a RAID which is why I asked the question of Paul in
> the first place.

My first RAID was with three Seagate economy 1.5TB drives in RAID 5, shortly
followed by three 1TB WD black drives in RAID 0. I never had the problems
you describe, though I rebuit the RAID5 several times as I was figuring
things out. (the 3TB RAID0 was for some heavy duty scratch space.)

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