Re: howto spin down a SCSI HD?

[Rik van Riel]

On Thu, 6 Jan 2000, Andreas Bombe wrote:
> On Wed, Jan 05, 2000 at 10:28:43AM -0500, Richard B. Johnson wrote:
> > On Wed, 5 Jan 2000 [e-mail] wrote:
> > 
> > > I'm getting crazy by the sound of my 3 1Gb SCSI hd's
> > > how can i spin them down so they make less noise?
> > 
> > The START/STOP unit command (0x1b) will, with some devices, shut down
> > the drive motor. However, this command is optional and not implemented
> > on all drives.
> 
> And it is probably not best practice to spin down SCSI disks
> often.  Unlike IDE disks, SCSI disks are targetted at the server
> market where disks are ideally running 24 hours a day.

This is not true any more. If there's both a SCSI and IDE
model of the same hard drive, you can bet that they both
use the exact same drive mechanics. The only exception
here are the ultra-cheap-cut-all-corners IDE-only drives
and the rediculously-high-end SCSI-only drives...

What _is_ true, however, is that you cannot just turn off
a hard drive that's been running 24x7 for ages. When a
disk is turned off its heads go to the `parking zone', an
area of the disk which has a wavey surface so that the
heads can get rid of the dust they gathered without getting
stuck to the surface (sticktion).

However, a 24x7 drive often has gathered so much cruft on
the heads that it'll stick even in the parking zone. The
solution is to do a short (30 sec) poweroff and get running
again for a few minutes before the long poweroff. That time
the heads can shake off most of their dust without getting
the time to stick...

> This might have changed with current disks where IDE and SCSI versions

It has, as usual all the rules have changed :)

cheers,

Rik
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