Den 9 juni 2017 21:40 skrev Matthias Leopold <matthias.leopold@meduniwien.ac.at>:
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?

Seems to me that the snapshot operation, where the host needs to save all of the VM memory chokes the storage pipe, the host becomes "unresponsive" from engine's point of view and all goes up shit creek. How is the hypervisor connected to the storage, in more detail?

/K


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.

it looks like some obvious configuration botch or performance bottleneck
to me. can it be linked to the network roles (management and migration
network are on a 1 GBit link)?

i'm still new to this, not a lot of KVM experience, too. maybe someone
recognizes the culprit...

thx
matthias
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