cluettr
Contributor
Contributor

Evaluating ESXi, Question about a Hardware Failure Scenario

I'm curious what happens to a VMWare guest when the host fails. If I have a VMWare ESXi host running on a server where the vmdk's reside on (and are booted from) an iSCSI SAN or an iSCSI/NFS NAS what happens when the host's hardware fails? An example would be a RAID 5 disk failure. Should the VM still be intact and OK so it can just be moved to a new host server? Would the vmdk potentially have suffered corruption even though the disks local to the server are not hosting the VM?

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3 Replies
eeg3
Commander
Commander

If you're using iSCSI for the virtual machine's storage and you're utilizing HA, the machines will be restarted upon a host failure. If you're not using HA, you will have to manually power them on to a new host but the virtual machines' disks will stay intact. The guest filesystem could still run into issues in the same way if you pulled the power on a physical server and everything wasn't written to disk (writes that haven't been written to disk yet will be lost when the power was removed).

If the virtual machines are stored on Local Disks on the host itself, the machines will go down upon a host failure. If the host's storage fails irreparably and the virtual machines reside on that storage then they will be lost.

Blog: http://blog.eeg3.net
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a_p_
Leadership
Leadership

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Josh26
Virtuoso
Virtuoso

Any unclean shutdown has some degree of potential for corruption.

The literature always suggests it's a seamless failover, 95% of the time it is. I'm sure you've seen physical servers experience issues after a power cable pull - this is the same as the scenario you describe.

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