Hi,
Here is my original question:
I have a Alpha 255 running DU4.0.
It has a "Power Management" Configuration.
One of the options is to Spin the Disk's Down after
a period of Non-Usage.
I am curious whether this is a good idea for UNIX
systems. That is, will the Hard Disk be damaged by
it constantly been spun down & up ??
Is it better to have the disk spinning all the time ??
Here are the replies:
> From: alan_at_nabeth.cxo.dec.com
> Unless considerations have been made for saving power else-
> where in the kernel it seems likely that general housekeeping
> and update I/O will keep many disks constantly spinning anyway.
> But, it depends on the timer threshold that is used to decide
> a disk has been idle. If suitable over the update time, then
> it won't ever be idle enough to spin down. Disks that don't
> have file system on them, won't have such house keeping I/O
> the timer (if settable) can be set appropriately.
>
> Spin-up probably puts the most stress on the motor that
> keeps the platters spinning. Unless a disk is designed
> for constant spin-up/spin-down cycles, then the stress
> could shorten the lifetime. And, from a point of view,
> spinning up is probably much more expensive than just
> letting it spin a constant speed.
>
> From: "Dr. Tom Blinn, 603-881-0646" <tpb_at_zk3.dec.com>
> Most modern hard disks can handle this just fine. In fact, you might find
> that PC operating systems (like, say, Windows 95) do this without telling
> you, as part of a power management regimen.
>
> Old disks might not be happy with this. In fact, some really old SCSI disks
> may not respond to a "spin up" command after a "spin down" is issued. There
> will be "per disk" controls in a future release to deal with this.
>
> As long as the disk is really idle for long periods of time (the assumption
> being that if a disk has been idle for a long time, it's likely to remain
> idle for some time to come, so that you will NOT see a cycle of "spin up, do
> a few I/Os, spin down", there's no reason to keep it spinning.
>
> Tom
> From: Paul Henderson <pgh_at_unx.dec.com>
> When designing this feature, it was found that the spin down does not
> affect the disk reliability. In fact, it may even help since the wear
> and tear on motors is much less. I've been running it on my AS255 for
> a couple of years now (I have one of the prototype machines) and never
> have had a disk problem. I also have been running it on older disks
> (RZ56s) and see no problems. The main reason for providing this
> functionality is to save energy. On my workstation, my disks are spun
> down from 6pm to 8am, thus saving half a day of power consumption. It
> adds up!
>
> It is also estimated that if every computer user simply turned off
> their monitors at night (this doesn't affect an Alphastation login),
> the output of six power plants would be saved each year. That's a lot
> of CO2. Add to that spinning down all the disks that are infrequently
> used, and you get truly significant power savings.
I guess it is safe to use the feature.
Thanks
,,,
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Received on Wed May 07 1997 - 08:00:03 NZST