Paolo, Please recall you had sent me the link below to a kernel patch to allow 'qemu-nbd' to flush to disk. The patch was applied with good success.
However, recent testing indicates that filesystem corruption issue I am seeing seems to be tied to large (>500mbyte) filesystem writes. I also observe the kernel 'flush' thread approaching 100% cpu at times, and i/o wait % as reported by 'top' increasing sharply during the copy/write. Was wondering if perhaps there are any special kernel config options that I may be missing for 'nbd', or any other information that might help. Best regards, Mark Trumpold >-----Original Message----- >From: Paolo Bonzini [mailto:paolo.bonz...@gmail.com] On Behalf Of Paolo >Bonzini >Sent: Wednesday, September 12, 2012 11:30 PM >To: Mark Trumpold >Cc: qemu-devel@nongnu.org >Subject: Re: 'qemu-nbd' explicite flush to disk >Il 12/09/2012 23:28, Mark Trumpold ha scritto: >> So, I've been experimenting with 'qemu-nbd --cache=writeback ..' >> This nicely eliminates the 'checkpoint' issue; however, I have as >> yet been unable to explicitely flush things to disk -- which I would >>like to >> do just before a 'nilfs' snapshot. >The Linux kernel driver for NBD does not support flushes. Patches were >sent to the maintainer, but he never applied them. >You can get them at >http://thread.gmane.org/gmane.linux.drivers.nbd.general/1108 and try >them. >> Subsequently I've been trying to call 'bdrv_co_flush(bs)' directly, but >>I can't >figure out how to dereference 'bs' for the call. >> >> I'm probably out in the weeds on this one. >> Any guidance would be greatly appreciated. >> >> I am running: >> qemu-1.2.0 >> linux kernel 3.3.1 >> >> Thank you, >> Mark Trumpold
