[mythtv-users] Putting the Computer to sleep (low-power)

Nigel Metheringham nigel.metheringham at dev.intechnology.co.uk
Mon Aug 1 14:20:04 UTC 2005

On Mon, 2005-08-01 at 07:10 -0700, chris at cpr.homelinux.net wrote:
> On Mon, Aug 01, 2005 at 01:16:49PM +0200, Marius Schrecker wrote:
> > I would also love to know how to get this to work in Linux. It's not so
> > much putting the disk to sleep as keeping it there. I've never managed to
> > get a HD to powerdown (using hdparm) for more than half a second without
> > being woken up again. :(
> If you are using a journalled filesystem (virtually anything other than
> ext2) then you need to mount using the noatime option so that the
> journal flushes don't trigger atime updates.

The advice here is fine - mounting noatime reduces the writes that are
generated to the disk (and in many cases people will never ever notice
that atime is missing - its a relatively specialised requirement).
However this has nothing to do with journalling.  The journal is outside
the filesystem (even on very old ext3 where the journal exists as a
special visible file the atime updates didn't apply to it), so
journalling does not affect atime flushes.  

However there is a load of standard system activity which will result in
(say) a read of the (buffer cached) root directory of a filesystem -
this is a read of the directory so now the directory atime has to be
updated, resulting in a disk write.  Thats why turning atime off is a
good idea for machines that wish to power down the disks.


[ Nigel Metheringham           Nigel.Metheringham at InTechnology.co.uk ]
[ - Comments in this message are my own and not ITO opinion/policy - ]

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