Subject: Re: 1.4.1, APM, SCSI disk spin down how?
To: None <>
From: Hal Murray <>
List: current-users
Date: 07/26/2000 18:03:18
>                                                 I guess I would ask
> myself is power management going to save you as much money in power
> savings as a new drive would cost (probably not with SCSI)

I'm not interested in the cost of the power, but rather the noise 
and perhaps heat from a drive that isn't doing anything useful.

I'm thinking of a machine at home that is mostly idle.  With DSL 
or cable, it would be nice to leave the machine on but turn off the 
disks when they weren't being used. 

Perhaps the system disk would say spinning all the time and the backup 
or web disk would be turned on only when needed.

> 	Provided that all disk I/O is suspended somehow in the OS,
> remember that Unices are running sync every 30 seconds or so. You might

This is an area I don't understand.  Why does a disk that isn't doing 
anything need to get written to every 30 seconds?  I assume it's 
only updating the time-last-running.   Is there something fundamental 
going on that I don't know about?  If so what?

If I have two disks mounted but nothing is happenind, do both get 
written to every 30 seconds? 

Would it be possible/reasonable for update/sync to cooperate with 
the powerdown mechanisim?  I'm thinking of something like having 
a powerdown flag (per disk) and sync skips writing (to that disk) 
when the flag is set.  The flag would get cleared by the automagic 
power up needed for any "real" disk activity.