Dear Paolo,

Thank you very much. To execute the backup, I run a script. For the machine in question, it looks as follows:

#!/bin/bash
dt=`date +%y%m%d`
qemu-img snapshot -c gatewayb72 /kvm02/gatewayb72.img
qemu-img convert  -f qcow2 -O qcow2 /kvm02/gatewayb72.img /backup/gatewayb72$dt.img
qemu-img snapshot -d gatewayb72 /kvm02/gatewayb72.img
/bin/find /backup/* -mtime +100 -exec rm {} \;

Regards,

Michael


-----Ursprüngliche Nachricht-----
Von: Paolo Bonzini [mailto:pbonzini@redhat.com] 
Gesendet: Mittwoch, 19. November 2014 12:42
An: Prof. Dr. Michael Schefczyk; qemu-devel
Betreff: "File too large" error from "qemu-img snapshot" (was Re: AW: Bug Repoting Directions Request)



On 19/11/2014 12:39, Prof. Dr. Michael Schefczyk wrote:
> Dear Paolo,
> 
> thank you very much for your prompt reply.

Hi,

please keep the replies on the mailing list.  I've added the qemu-devel mailing list, where more people should be able to see the message and hopefully reply with something helpful.

Also, how do you do the backups?

Paolo

> For example, I have a guest named "gatewayb72.img" where the backup failed. If I thereafter try to create or delete a snapshot, the following reply occurs on the command line:
> 
> 
> [root@linuxhost2 kvm02]# qemu-img snapshot -d gatewayb72 
> /kvm02/gatewayb72.img
> qemu-img: Could not open '/kvm02/gatewayb72.img': Could not read 
> snapshots: File too large
> 
> 
> If I want to reboot that machine, I get the following error:
> 
> 
> Fehler beim Starten der Domain: Interner Fehler: Prozess wurde während 
> der Verbindungsaufnahme zum Monitor beendet : qemu-kvm: -drive 
> file=/kvm02/gatewayb72.img,if=none,id=drive-virtio-disk0,format=qcow2,
> cache=none: could not open disk image /kvm02/gatewayb72.img: Could not 
> read snapshots: File too large
> 
> 
> Traceback (most recent call last):
>   File "/usr/share/virt-manager/virtManager/asyncjob.py", line 100, in cb_wrapper
>     callback(asyncjob, *args, **kwargs)
>   File "/usr/share/virt-manager/virtManager/asyncjob.py", line 122, in tmpcb
>     callback(*args, **kwargs)
>   File "/usr/share/virt-manager/virtManager/domain.py", line 1220, in startup
>     self._backend.create()
>   File "/usr/lib64/python2.7/site-packages/libvirt.py", line 698, in create
>     if ret == -1: raise libvirtError ('virDomainCreate() failed', 
> dom=self)
> libvirtError: Interner Fehler: Prozess wurde während der 
> Verbindungsaufnahme zum Monitor beendet : qemu-kvm: -drive 
> file=/kvm02/gatewayb72.img,if=none,id=drive-virtio-disk0,format=qcow2,
> cache=none: could not open disk image /kvm02/gatewayb72.img: Could not 
> read snapshots: File too large
> 
> 
> Based on the facts I can see, the file is not too large. When reading the first error, the file size was 13.8 GB, while the limit is 14.5 GB. The same does also happen with files which are only, for example 6 GB big, while their limit is also 14.5 GB. Therefore, I think that the "file too large" really stands for something else.
> 
> Can I provide any additional information?
> 
> Regards,
> 
> Michael
> ___________________________________________________________
> Technische Universität Dresden
> Fakultät Wirtschaftswissenschaften
> Lehrstuhl für Entrepreneurship und Innovation Prof. Dr. Michael 
> Schefczyk
> D-01062 Dresden
>  
> Fon: +49-3 51-4 63-3 68 81
> Fax: +49-3 51-4 63-3 68 83
> www.gruenderlehrstuhl.de

>> Since some months ago, I am facing the problem, that backups fail 
>> unpredictably. A failed backup does not generate a backup file and 
>> thereafter, snapshots can no longer be created or deleted and the 
>> guest cannot be started anymore. The resulting error message is "File 
>> too large".
> 
> Who is reporting the "File too large" error?  Can you please include the error in full detail?
> 
> Paolo
>