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List:       user-mode-linux-user
Subject:    Re: [uml-user] about the kernel switch
From:       Jeff Dike <jdike () addtoit ! com>
Date:       2005-04-28 21:33:14
Message-ID: 20050428213314.GB26596 () ccure ! user-mode-linux ! org
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On Fri, Apr 29, 2005 at 10:33:26PM +0200, Blaisorblade wrote:
> On Tuesday 26 April 2005 10:52, Jack wrote:
> > hi all .
> >
> >     i am confused with the switches of the kernel .
> >
> >    could someone tell me the ubd0s  the "s" append means what ?
> Access that ubd device synchronously, which is needed for journaled 
> filesystems consistence.

More specifically, the driver will do O_SYNC I/O to the host for that device.

Hurts performance, but if you're paranoid about write ordering being 
preserved from the UML down to the disk, you might want to think about it.

If the host crashes in the middle of a journalled UML transaction, then 
possibly the filesystem could be corrupted.  I've never heard of this
happening, though.

				Jeff


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