Re: SCSI disk driver module spin-up
Albert Cahalan (albert@ccs.neu.edu)
Sun, 25 Feb 1996 21:39:59 -0500 (EST)
>>>> I wonder if it might not be more useful to only spin up drives
>>>> when they are actually needed, be it at mount time or even only
>>>> upon actual access. This might be especially useful for drives
>>>> used mainly as backup storage (e.g. to keep source trees that
>>>> only need to be accessed every other week)...
>>>
>>> I guess I am not really in favor of spinning down disks all the
>>> time. Most of the wear and tear that decreases the lifetime of a
>>> disk is at startup and shutdown, so unless there are power management
>>> reasons (i.e. on a laptop), I think it is probably better to simply
>>> leave the disks spinning all the time.
>>>
>>> In principle, it would probably not be that harmful to perform
>>> spinup/spindown on mount/unmount. Having an idle timer seems like a
>>> dangerous idea to me, as you could wear out a disk in a real hurry.
>>
>> Well, what about a _long_ timeout?
>>
>> Always spindown after 26 hours without an access.
>> Spindown after 1 hour if the last access was umount.
>>
>> (the 26 is in case you do something one a day and are late)
>
> It seems to me that the question should be whether there is a good reason
> to spin the drive down IN THE PARTICULAR CIRCUMSTANCES. The
> crash-rip-grind-tear-scrape of the spindle bearings during a start-stop
> will almost certainly subtract from the remaining life of a drive. The
> heads will also give up a few of their N lives. But with a properly cooled
> drive, there is very little wear and tear during normal operation.
Perhaps your drive is properly cooled - many are sandwitched between
the floppy drive and a pile of ribbon cables.
> But for the rest of us, I think that the way to a long-lived machine is to
> let it run 24x7, especially the drives. Monitors are a different story as
Well, what number of hours running causes the same wear as one spinup?
Determine this (buy 10000 drives and run them...), then spindown at
10% of that time because most drives are not well cooled.
I do think 26 hours is good. If you do not use the disk for 26 hours,
it is likely that you will not use it again any time soon.
(about partition tables: you don't _need_ to read them all)