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Re: XFS write cache flush policy

To: Stan Hoeppner <stan@xxxxxxxxxxxxxxxxx>
Subject: Re: XFS write cache flush policy
From: Matthias Schniedermeyer <ms@xxxxxxx>
Date: Thu, 20 Dec 2012 11:18:23 +0100
Cc: xfs@xxxxxxxxxxx
In-reply-to: <50D2A6C0.3070100@xxxxxxxxxxxxxxxxx>
References: <20121216111046.GA16756@xxxxxxx> <20121216204847.GN9806@dastard> <20121216232251.GA20370@xxxxxxx> <20121217232441.GA5031@dastard> <20121218003438.GB30736@xxxxxxx> <20121218202914.GC15182@dastard> <20121219010445.GA24313@xxxxxxx> <20121219224328.GN15182@dastard> <20121220014014.GA15121@xxxxxxx> <50D2A6C0.3070100@xxxxxxxxxxxxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
On 19.12.2012 23:48, Stan Hoeppner wrote:
> On 12/19/2012 7:40 PM, Matthias Schniedermeyer wrote:
> 
> > I had thought about issuing a 
> > 'sync', because the previous incarnation of the bug flashed before my 
> > inner eye. But by the time i had shutdown X and got to the 
> > command-prompt i had already forgotten to type 'sync' and went straight 
> > for 'reboot'
> 
> When did you last read the man pages for reboot and shutdown?  reboot
> issues a sync automatically unless you specify
> 
> -n     Don't sync before reboot or halt. Note that the kernel and
> storage drivers may still sync.
> 
> (note the disclaimer)
> 
> and even though the shutdown man page doesn't state so explicitly, I'm
> pretty darn sure that shutdown issues a sync before halting or rebooting.
> 
> Thus, you shouldn't have to manually call sync before issuing your
> favorite system restart command.  If sync isn't being called, maybe
> there's an issue with the versions of these commands shipped with your
> distro, or other type of problem.

That's strange, i looked into the source of /sbin/halt and it does 
contain a call to 'sync'.

So it either didn't work, or i hit the umount-bug that David mentioned.

When i rebooted to 3.7(.0), from a buggy 3.6.2, i 'sync'ed manually 
before rebooting and also manually 'umount'ed all "physical" FSes except 
the rootfs and this time i didn't get a corruption. All 
mount-syslog-lines for the 3.7 boot say the filesystem was clean.

So when it is time to reboot to 3.7.2, which hopefully contains the 
bugfix, i still intent to do a wetware (half-)shutdown before the actual 
'reboot'. The statistic is 2 out of 3 in favor of corruptions in the 
last 3 reboots of this particular computer.



-- 

Matthias

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