On Mon, Nov 18, 2002 at 11:07:44AM -0700, Bob Proulx wrote:
> Ron Johnson <ron.l.johnson@cox.net> [2002-11-18 11:45:01 -0600]:
> > > this problem, but generally using a journaling file system on a laptop
> > > is a Bad Idea (TM).
> >
> > Because of battery drain?
>
> Yes. One way to reduce battery drain is to have the hard drive
> powered off. A typical laptop with the disk powered down can run for
> ten times as long as one with the disk powered up, YMMV. RAM will
> either be a real ram disk or a buffer cache.
>
> Operating off of a ram disk with the hard drive powered off I could
> run an old laptop of mine for more than 8 hours on battery. But if
> the filesystem keeps the hard drive awake by writing to it every few
> seconds then you can't power it down and can't save the power and you
> are stuck with much reduced battery life. In my case less than an
> hour.
>
> BTW... I am battling this same problem myself with a fresh install on
> my laptop. I can see it is going to take me a while to figure out the
> tuning to get it back into long life mode again. I can't get my disk
> to power off either.
I haven't tried this, so caveat emptor.
When you format an ext3 disk, you can specify the journal on another
device. If you put the journal on a RAM disk, you should be able to
spin the disk down. Obviously, the potential for disaster here is
huge; if the laptop goes down for the count you just lost your
journal. If your laptop autosuspends or hibernates when the battery
is about to croak, that might improve the chances of this working.
The other problem I can see is that you'd have to mount the ramdisk
before you mounted the ext3 partition, and restore the journal to it.
When you shut down, you'd have to save the contents of the journal
somewhere before you unmounted the journal.
All in all, this seems stupid; the point of the journal is to save you
after catastrophic failure. Therefore if you desire long battery life
from your laptop, I think ext3 is not the correct filesystem choice.
ext2 with noflushd is a better choice.
Does anyone have experience with the other journaling filesystems like
reiser or xfs on a laptop?
--
Nathan Norman - Incanus Networking mailto:nnorman@incanus.net
Tell me and I'll forget; show me and I may remember; involve me
and I'll understand.
-- Chinese Proverb
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