VM state after host power failure

[willymaykett]

Hello,

If a vm is running on a host, and that host suddenly powers off dirty, like a power failure or an remote access card powering down the server because of a fault, overtemp etc, what happens to the vm?

My guess is the vm is effectively hard, dirty powered off too, and if HA is configured, etc it will do a full power on sequence. Or will it restart on a new server and automatically be in the same power on state with same memory and cpu states before the host dropped dead? So if I had a RDC connection to a windows server vm, and the host suddenly died, and it restarts, would I reconnect to the same session state immediately prior to the host failure?

Thanks

[Mouhamad]

Assume that this is a physical machine and not a VM. What will happen?

The answer is, whatever applies to a physical machine apply here to a VM..

You might have an OS failure because of the dirty shutdown, but you will never be able to have the same console since it will be killed when the vm is dead or restarted.

[willymaykett]

Thank you for the response.

I was always under the impression that if a host abruptly failed, so did the vm and it would be restarted, just like a normal physcial machine. However, I heard some one mention that esx keeps the current cpu and memory state always on disk with the vm, so that the restart on the new host would be "instantaneous" with no loss of memory /cpu/disk state or data and you can keep on runnign as if nothing happenned.

So I was correct in saying that the vm has been restared and there is no possibility of it being in the same state?

[Sreejesh_D · Accepted solution]

when ESX\ESXi fails due to power failure:

No HA configured:

1. all VMs will also will face the abrupt shutdown. VMs will lose the runtime data and all communication (including RDP connectivity) will be interrupted.

HA configured:

1. VMs will be powered-on on a different host. However, its same as a VM reset, we will lose the unsaved data.

VMware FT:

we can ensure 100% uptime for a VM using the feature VMware Fault Tolerance. In case of host failure, the next moment secondary VM in FT will take over. More details on FT are available in following link.

http://www.vmware.com/products/fault-tolerance/overview.html

[willymaykett]

thank you for confirming.

I was pretty sure HA on is own won't do it, but FT will.

Thanks