I have a question. Lately, for some reason we experience problems with our hypervisors. In a way that they suddenly appear to lose connection to a storage domain and start migrating the VM's. But if you can see it during the day and you just press the green arrow on the hypervisor (up) they just come back online and pretend that nothing happend...

These are the kind of  log lines:

Thread-18::ERROR::2016-01-05 07:39:11,170::sdc::154::Storage.StorageDomainCache::(_findUnfetchedDomain) looking for domain e1bbe4ab-3717-4a9a-ada2-9d175ab38262