At approximately 13:45, one of our Hyper-V hosts suffered a software crash, which caused the machine to 'blue screen'. This caused all the virtual machines (VMs) running on this host to power off, causing the loss of some Ecommerce sites.

Immediate steps were taken to restart the Hyper-V host and the machine came back, but then crashed again with the same issue.

We then took the decision to invoke our recovery process and start to boot up replicas of the affected VMs on other Hyper-V hosts. Some of these replicas took additional work to get them running, but all VMs were available again by 16:00.

The failure of the Hyper-V host was unexpected. We have established that it was a component of Hyper-V that crashed, but we will be undertaking an investigation to determine the root cause and any necessary follow-up actions.