Re: [Qemu-devel] Possible disk corruption with virtIO?

[Stefan Hajnoczi]

On Sat, Apr 14, 2012 at 2:31 PM, Prateek Sharma <address@hidden> wrote:
>   I am writing to ask whether there is any possibility of silent data
> corruption with virtIO/qemu.
> My files inside the guest are getting zeroed out. Specifically, bytes
> 512 to 4096 on some files are being zeroed out. (some 60K files out of
>  5Million are showing this so far).  The virtual disk is a file on
> ext4 (size of file is 1TB), and i am using virtio, aio-threads=native,
> and cache=none. The disk having the virtual disk is on mdadm
> raid1---so i am guessing possibility of disk corruption is low

Did you check the corruption by mounting the image file on the host
while the VM is not running?  This we you can be sure that there is no
bug that causes the guest to "see" zeroes.  If you see the zeroes
inside the guest we can't be 100% sure that the image file itself
contains them.

Can you describe the guest configuration?  Guest operating system?
Application/mail server?  Which files are being corrupted?  Is I/O
constantly being issued by the guest or does the corruption appear
even when the files are not being accessed?  Basically anything that
can help spot a pattern here.

Stefan