[ kvm-Bugs-2490866 ] repeatable corruption with qcow2 on kvm-79

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Bugs item #2490866, was opened at 2009-01-07 05:10
Message generated for change (Comment added) made by roy-anonymous
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Category: qemu
Group: None
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: Adrian Bridgett (abridgett)
Assigned to: Nobody/Anonymous (nobody)
Summary: repeatable corruption with qcow2 on kvm-79

Initial Comment:
Creating a qcow2 image, mkfs.ext3, sometimes mounting it would fail immediately, but in all cases it would corrupt (overwritten with zeros) after starting up backuppc on it.   This is KVM-79 on a Debian lenny host and guest.

This occured using virtio or not.  Swapping to a raw file or LV worked flawlessly.  I've tested the box with memtest and I don't have issues elsewhere but I've seen corruptions on other images.  host and guest are both 2.6.26-1-adm64 kernel (debian lenny) I'm running 32-bit userspace everywhere.  Dual core Intel Core2 E6300.

I see KVM-81 has "improve qcow2 data integrity with cache=writethrough" which _might_ be what I'm hitting - but I can't find more details about this to check (and backport patch to debian package or wait for newer debian package).

thanks.

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Comment By: roy anonymous (roy-anonymous)
Date: 2009-01-08 01:14

Message:
I am not quite sure it's true or not, for my case, I get corruption if I
have a new FC9 Guest installation with qcow2 with virtio_blk. But it won't
have any problem if I install with a FC8 qcow2 installation, then upgrade
to FC9 with virtio_blk

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Comment By: Laszlo Dvornik (ldvornik)
Date: 2009-01-07 15:42

Message:
Same problem here.

With Lenny and vanilla 2.6.28 kernel, with KVM 79, and with KVM 82 user
tools.
Tried with KVM 82 module compile for 2.6.28 and with 2.6.28 builtin KVM
sources.
32-bit userspace and kernel, Intel C2D T7100.

Another effect:
With empty qcow2, vmdk disk image formats, when I try to create a
partition and save the new partition table, they can't save it until
reboot. With raw image format there is no such problem.

I liked to try with qcow, but:
qemu: could not open disk image teszt.qcow

I switched all of my disk images to raw, until the problem fixed.

PS: The host filesystem is ext4, but I tested under ext3 filesystem too
and the problem wasn't disappeared.

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