[ovirt-users] trouble when creating VM snapshots including memory

[Matthias Leopold]

Am 2017-06-11 um 10:11 schrieb Yaniv Kaul:
> 
> 
> On Fri, Jun 9, 2017 at 3:39 PM, Matthias Leopold 
> <matthias.leopold at meduniwien.ac.at 
> <mailto:matthias.leopold at meduniwien.ac.at>> wrote:
> 
>     hi,
> 
>     i'm having trouble creating VM snapshots that include memory in my
>     oVirt 4.1 test environment. when i do this the VM gets paused and
>     shortly (20-30s) afterwards i'm seeing messages in engine.log about
>     both iSCSI storage domains (master storage domain and data storage
>     where VM resides) experiencing high latency. this quickly worsens
>     from the engines view: VM is unresponsive, Host is unresponsive,
>     engine wants to fence the host (impossible because it's the only
>     host in the test cluster). in the end there is an EngineException
> 
>     EngineException:
>     org.ovirt.engine.core.vdsbroker.vdsbroker.VDSNetworkException:
>     VDSGenericException: VDSNetworkException: Message timeout which can
>     be caused by communication issues (Failed with error
>     VDS_NETWORK_ERROR and code 5022)
> 
>     the snapshot fails and is left in an inconsistent state. the
>     situation has to be resolved manually with unlock_entity.sh and
>     maybe lvm commands. this happened twice in exactly the same manner.
>     VM snapshots without memory for this VM are not a problem.
> 
>     VM guest OS is CentOS7 installed from one of the
>     ovirt-image-repository images. it has the oVirt guest agent running.
> 
>     what could be wrong?
> 
>     this is a test environment where lots of parameters aren't optimal
>     but i never had problems like this before, nothing concerning
>     network latency. iSCSI is on a FreeNAS box. CPU, RAM, ethernet
>     (10GBit for storage) on all hosts involved (engine hosted
>     externally, oVirt Node, storage) should be OK by far.
> 
> 
> Are you sure iSCSI traffic is going over the 10gb interfaces?
> If it doesn't, it might choke the mgmt interface.
> Regardless, how is the performance of the storage? I don't expect it to 
> require too much, but saving the memory might require some storage 
> performance. Perhaps there's a bottleneck there?
> Y.

i shot myself in the foot by also playing around with network QoS and 
forgetting about it.... no wonder the network chokes when i tell it to 
do so. without randomly applied QoS profiles snapshots work perfectly ;-)

thx
matthias