Messages in this thread | | | Date | Fri, 3 Apr 2009 14:42:08 +0100 | From | Matthew Garrett <> | Subject | Re: Ext4 and the "30 second window of death" |
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On Thu, Apr 02, 2009 at 08:08:36PM -0700, david@lang.hm wrote: > On Fri, 3 Apr 2009, Matthew Garrett wrote: > >Well, yes, the administrator could hate the user. They could achieve the > >same affect by just LD_PRELOADING something that stubbed out fsync() and > >inserted random data into every other write(). We generally trust that > >admins won't do that. > > then trust the admins to make a reasonable decision for or with the user > on this as well.
What a reasonable decision is here depends on what software the user is running. There simply isn't a reasonable default other than to allow fsync() to work. Changing requires auditing every single piece of code the user may run.
> >There's various circumstances in which it's beneficial. The difference > >between an optimal algorithm for typical use and an optimal algorithm > >for typical use where there's an fsync() every 5 minutes isn't actually > >that great. > > mixing some sub-threads a bit to combine thoughts > > you object to calling something like this 'laptop mode' > > Ted's statements about laptop mode indicate that he believes that it > delays writes for a configurable time rather than accelerating writes.
As I said, the code is pretty easy to read.
(snip)
> thoughts?
I've certainly got no objection to the addition of a mode that changes the behaviour of fsync() - personally I think it would be an error for almost anyone to use it, but that's really up to the individual situation. But it would have a different goal to the existing laptop-mode and so should have a different name in order to avoid confusion.
-- Matthew Garrett | mjg59@srcf.ucam.org
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