----- Original Message ----- > From: "Paolo Bonzini" <pbonz...@redhat.com> > To: "Andrew Martin" <amar...@xes-inc.com>, "Stefan Hajnoczi" > <stefa...@gmail.com> > Cc: "qemu-devel" <qemu-devel@nongnu.org> > Sent: Tuesday, August 26, 2014 2:03:18 AM > Subject: Re: Using cache=writeback safely on qemu 1.4.0 and later > > > In the case of the files uploaded by apache2, they were added to the server > > days > > before the power outage, so it seems like there would have been ample time > > for > > those changes to have been flushed. > > Remember that cache=writeback has a huge cache, whose size is several > gigabytes. > > At some point there was a QEMU bug that caused the guest not to do > fsyncs. It was fixed by commit ef5bc96268.
Paolo, Thanks for the info about this bug - I am using QEMU 1.4.0 (released on 02/15/13) and ef5bc96268 was added on 09/20/13, so the bug had not been fixed in the version of QEMU I am using. I have had trouble reproducing it on-demand - was there specific behavior you used to reproduce it, or just the lack of fsyncs or fdatasyncs when stracing the QEMU process when using cache=writeback? Thanks, Andrew
