Disk power-down not possible

[Andreas Mohr]

Hi,

On Tue, Jan 01, 2008 at 02:45:13PM +0100, Peter Ganzhorn wrote:
> Hi,
> 
> I've tried to save some power with my laptop by powering down my disk 
> via "hdparm -y /dev/sda". The disk stops spinning immediately but will 
> start up within 5 seconds or less.
> To find out what's keeping the disk busy I got me blktrace and blkparse 
> and it seems the following processes keep the disk busy all the time:
> 
> swapper
> pdflush
> xfssyncd
> xfsbufd
> 
> Is there any way to suspend those processes if I want to power down my disk?

You probably need to enable linux/Documentation/laptop-mode.txt
(but in this case watch those hdparm -B settings!!! 600000 head unloads
may already kill a drive, judging from mfct. specifications!),
also you perhaps need to adjust the dirty flush setting as suggested
by powertop (suggested to increase from 5 to 15 seconds,
dunno what the setting was called exactly).

And I wouldn't do this unless one achieves notebook HDD powerdown lengths above
2 minutes at least, otherwise I'd be concerned about HDD health.
(better watch those smartctl SMART usage count increments!)

Andreas Mohr