linux-ext4 - Re: Sync does not flush to disk!?

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Message-id: <4FD1E47D.2050908@shiftmail.org>
Date:	Fri, 08 Jun 2012 13:39:41 +0200
From:	Asdo <asdo@...ftmail.org>
To:	Asdo <asdo@...ftmail.org>
Cc:	linux-raid <linux-raid@...r.kernel.org>, linux-ext4@...r.kernel.org
Subject: Re: Sync does not flush to disk!?

On 06/08/12 11:53, Asdo wrote:
> .....
> Then I tried to do :
>
> for i in /dev/md? /dev/sda /dev/sdb ; do blockdev --flushbufs $i ; done
> ....
> and NOW it is seeing the changes.

After some further tests:
Flushbuf'ing just the MD devices only, generated an even more 
intermediate situation in which the file being changed assumed garbage 
content coming from another old file.
Flushbufing just /dev/sda /dev/sdb has worked a few times I tried. I'm 
not sure that it is enough in general.
Flushbufing everything appears to work reliably.

Still I am puzzled. Wasn't "sync" from bash enough to commit to disk 
even in case of power failure?

Or is there any chance that KVM "sees" a version of sda and sdb which is 
actually *older* than the actual content on the platters?

Thank you
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