[Qemu-discuss] Source of QCOW Image Corruption

[Andrew Martin]

Hello, 

I have two KVM virtual machine nodes in a high-availability cluster using 
Pacemaker + Heartbeat on Ubuntu 10.04 Server amd64. This cluster hosts a single 
Ubuntu 10.04 VM which uses a qcow2 image file, myvm.qcow2, with a backing file, 
backingfile.qcow2. This morning, the VM suddenly powered off. I attempted to 
start it again with virsh start domain, but it would only start briefly and 
then power off again. I checked the qcow2 disk image and found countless 
corruption errors: 

address@hidden:/mnt/storage/vmstore/disks# qemu-img info myvm.qcow2 
image: myvm.qcow2 
file format: qcow2 
virtual size: 9.8G (10485760000 bytes) 
disk size: 13G 
cluster_size: 65536 
backing file: backingfile.qcow2 (actual path: backingfile.qcow2) 
Snapshot list: 
ID TAG VM SIZE DATE VM CLOCK 
1.5G 2056-05-05 21:01:212795663:45:42.642 
/archive/1006/20100627000/2il_root/save/archive/1002/20100204005/1 743M 
1995-08-16 12:47:352289751:06:20.183 
address@hidden:/mnt/storage/vmstore/disks# qemu-img check myvm.qcow2 2>&1 | 
head 
ERROR OFLAG_COPIED: offset=80000002047d0000 refcount=0 
ERROR OFLAG_COPIED: offset=8000000212e50000 refcount=0 
ERROR OFLAG_COPIED: offset=80000001ffde0000 refcount=0 
ERROR OFLAG_COPIED: offset=80000001ff710000 refcount=0 
ERROR OFLAG_COPIED: offset=8000000216ec0000 refcount=0 
ERROR OFLAG_COPIED: offset=8000000206db0000 refcount=0 
ERROR OFLAG_COPIED: offset=80000001ff720000 refcount=0 
ERROR OFLAG_COPIED: offset=80000001ffdf0000 refcount=0 
ERROR OFLAG_COPIED: offset=8000000212e60000 refcount=0 
ERROR OFLAG_COPIED: offset=8000000212e70000 refcount=0 
address@hidden:/mnt/storage/vmstore/disks# qemu-img info backingfile.qcow2 
image: backingfile.qcow2 
file format: qcow2 
virtual size: 9.8G (10485760000 bytes) 
disk size: 4.8G 
cluster_size: 65536 
address@hidden:/mnt/storage/vmstore/disks# qemu-img check backingfile.qcow2 
No errors were found on the image. 


I had this happen a month ago on the same machine but a different physical 
drive, so I do not believe it to be a physical disk failure. I can find nothing 
in /var/log that gives any more information related to this corruption. What 
other debug information can I provide to diagnose why these images are getting 
corrupted and taking these running VMs offline? 


Thanks, 


Andrew Martin