graphic: 0.899
device: 0.726
performance: 0.715
semantic: 0.526
other: 0.450
socket: 0.444
PID: 0.412
permissions: 0.378
vnc: 0.366
boot: 0.360
debug: 0.344
network: 0.341
files: 0.196
KVM: 0.126

Snapshot usage makes qcow2 image unusable due to large tables

To reproduce with 0.9.1 and svn:
- Create a 20G (or some size much greater than system RAM) qcow2 image
- Inside VM, install some OS, formatting whole drive
- Create snapshot with savevm
- Inside VM, reformat and reinstall OS
- Create snapshot with savevm
[...]

Eventually, qemu crashes, then neither qemu-img nor qemu can open the image because memory is exhausted.  The reason is that the whole refcount_table is loaded into memory, and this refcount_table has now become much bigger than the size of memory.

The refcount_table really needs to be loaded and used in fixed size chunks to avoid this problem.

Alternatively, there needs to be a way to "rollback" a snapshot without loading the whole disk image normally, so that a snapshot which has made the image unusable in this way can be reversed.

Hi,

Could you please let us know whether this is still a problem and if it isn't, lets close this bug.

 In addition, you haven't listed which version of qemu-kvm you are running. I am guessing it is something Ubuntu based based on the version number, but since not all of us are running Ubuntu it would be useful to have more details.

Thanks,
Jes


[Expired for QEMU because there has been no activity for 60 days.]