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Re: [Qemu-discuss] Source of QCOW Image Corruption

From: Jakob Bohm
Subject: Re: [Qemu-discuss] Source of QCOW Image Corruption
Date: Wed, 15 Aug 2012 19:37:01 +0200
User-agent: Mozilla/5.0 (Windows NT 5.2; WOW64; rv:14.0) Gecko/20120713 Thunderbird/14.0

Please note that qemu 0.12.3 is quite old now, but "long term
stability" OS distributions are defined by freezing all software
versions at some point in time, and then maintaining those
versions with cherry picked backported patches for 5 to 10
years, so this is normal.
However I guess that a lot of folks around here will simply
refuse to deal with such old software, because they believe
in the bleeding edge.
On 8/14/2012 10:54 PM, Andrew Martin wrote:
Some additional information: 

Cloning the VM disk image with qemu-img convert results in an image that appears to be error free and can be mounted successfully: 
# qemu-img convert myvm.qcow2 -O qcow2 test.qcow2 
# qemu-img check test.qcow2 
No errors were found on the image. 

Also, the following error is logged in /var/log/libvirt/qemu/myvm.log when attempting to start the VM: 
# tail /var/log/libvirt/qemu/myvm.log 
LC_ALL=C PATH=/usr/local/sbin:/usr/local/bin:/usr/bin:/usr/sbin:/sbin:/bin QEMU_AUDIO_DRV=none /usr/bin/kvm -S -M pc-0.12 -enable-kvm -m 8192 -smp 6 -name myvm -uuid 14a9dd6b-7a80-b286-8558-8c0c1f0324dc -chardev socket,id=monitor,path=/var/lib/libvirt/qemu/myvm.monitor,server,nowait -monitor chardev:monitor -boot c -drive file=/mnt/storage/vmstore/disks/myvm.qcow2,if=virtio,index=0,boot=on,format=qcow2,cache=none -drive file=/dev/drbd1,if=virtio,index=1,format=raw -drive file=/dev/drbd2,if=virtio,index=2,format=raw -net nic,macaddr=00:16:3e:32:35:82,vlan=0,model=virtio,name=virtio.0 -net tap,fd=55,vlan=0,name=tap.0 -chardev pty,id=serial0 -serial chardev:serial0 -parallel none -usb -vnc -vga cirrus 
char device redirected to /dev/pts/0 
pci_add_option_rom: failed to find romfile "pxe-virtio.bin" 
qcow2_free_clusters failed: Invalid argument 

These systems are running the stock Ubuntu 10.04 version of qemu-common, qemu-kvm, and kvm (0.12.3+noroms-0ubuntu9.19). 


----- Original Message -----

From: "Andrew Martin" <address@hidden> 
To: address@hidden 
Sent: Tuesday, August 14, 2012 1:53:44 PM 
Subject: [Qemu-discuss] Source of QCOW Image Corruption 


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: 
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? 


Andrew Martin 


Jakob Bohm, CIO, Partner, WiseMo A/S.  http://www.wisemo.com
Transformervej 29, 2730 Herlev, Denmark.  Direct +45 31 13 16 10
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