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Date:      Thu, 30 Apr 1998 12:45:14 -0400
From:      "Steve Sims" <SimsS@IBM.Net>
To:        "'Doug White'" <dwhite@resnet.uoregon.edu>
Cc:        <questions@FreeBSD.ORG>
Subject:   RE: Monitoring disk access
Message-ID:  <000001bd7457$5b51b4a0$64468094@Elvis.RatsNest.VaBeach.Va.Us>
In-Reply-To: <Pine.BSF.3.96.980429131702.13074H-100000@gdi.uoregon.edu>

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Doug - Do I interpret you correctly:  If APM is enabled in the kernel, it
explicitly prohibits the drive(s) from spinning down?

If I'm reading you correctly, the Power Management stuff *should* (not to
infer that somebody ought to make it so) allow the drives to idle down and
extend the "interrupt timeout" that you mention.

A couple of years back, I was playing with one of the first "green machines"
I'd ever seen (and it did let the drives spin down).  When the disk was hit,
it would (often) bark about timeouts, but it was innocuous - the FS
integrity was maintained.  I hacked (mumble, mumble.... wdc-"something")
that extended the timeouts and it seemed to work pretty good for the few
days that I was farting around.  IIRC, this was, like, a 1.1.5 system.

Sorry to be obtuse, but, to my mind, logic would indicate that enabling APM
in the kernel would activate an accommodation for spin downs, rather than
prevent them from ever happening!?!?

...sjs...

-----Original Message-----
From: Doug White [mailto:dwhite@gdi.uoregon.edu]
Sent: Wednesday, April 29, 1998 4:20 PM
To: Steve Sims
Cc: questions@FreeBSD.ORG
Subject: Re: Monitoring disk access


On Thu, 23 Apr 1998, Steve Sims wrote:

> But the problem remains that the disk doesn't ever spin down, even though
> all the APM stuff is enabled and the disk is set to spin down after 60
> seconds of inactivity.

If you have APM built in then it enables a command in the wdc driver that
explicitly disables disk spindown.  The wdc driver gets angry if it
accesses a spindown disk, it will spew errors about ``interrupt timeout''.

> I've got to believe that something is periodically touching the disk and
> that's enough to reset the sleep-mode timer.  Is there a way of checking
to
> see what's prodding the hard drive?

Run top and watch -- if a process uses the disk it's priority will jump
and it may show up in a `sbwait' state.

Doug White                              | University of Oregon
Internet:  dwhite@resnet.uoregon.edu    | Residence Networking Assistant
http://gladstone.uoregon.edu/~dwhite    | Computer Science Major




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