Re: Ext4 and the "30 second window of death"

From: Matthew Garrett
Date: Thu Apr 02 2009 - 21:22:32 EST


On Thu, Apr 02, 2009 at 06:17:12PM -0700, david@xxxxxxx wrote:
> On Fri, 3 Apr 2009, Matthew Garrett wrote:
>
> >On Thu, Apr 02, 2009 at 05:59:53PM -0700, david@xxxxxxx wrote:
> >
> >>is laptop mode
> >>
> >>A. "write everything now, don't delay writes" in the hope that the drive
> >>will be idle enough later to spin down
> >
> >laptop-mode doesn't delay writes. Ever.
> >
> >>or
> >>
> >>B. "delay all writes until later, then when the drive wakes up do all
> >>pending writes at that time" so that the drive can go to sleep in the
> >>meantime?
> >
> >Yes.
>
> you just contridicted yourself in these two statements.

That's because I'm horribly drunk and managed to confuse the order of
your statements. My substantive point stands - the laptop-mode code
doesn't delay writes, and it's pretty easy for anyone to prove this to
themselves. Neither of your options actually describe its behaviour.
--
Matthew Garrett | mjg59@xxxxxxxxxxxxx
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