The strangest thing happened to me yesterday.
I have a customer with a a server that has ESXi6 installed with 7 VM's. The server kept freezing every couple of days but came back online after rebooting, I think I've put this down to an old firmware revision on the DL380 G6 P410i Storage Controller which I've upgraded to the latest firmware file.
Anyway.... each time the only VM that would cause me a headache when rebooting the server was their Exchange 2010 VM. Each time the VM would lose it's name and show with it's vm path on the storage with (invalid) at the end.
So i deleted the VM from the inventory each time and recreated it using it's .vmx file. This worked fine the first few times, until the last two times where I would have to create a new VM using the "Custom" option, select the two disks, C: and E: drive from it's storage folder on the datastore and recreate it that way.
The last time really messed things up for me...
Some how when i recreated the machine, I booted it up and saw all the latest event logs were from 30/08/2015! It has reverted the Exchange server back to 30/08/2015, including all the mailboxes! The customers are going ape s**t at me because most of the users now have an empty mailbox because the VM has reverted back to when I first create it back in August (this was when I migrated all their inboxes from their old Exchange 2003 server).
My question is..... how would the VM have reverted back to the 30/08/2015?
I backup all my VM's using Veeam... When I reconnected the disks I definitely selected the two main .vmdk files for the C: drive and E: drive. There are a few what looks like snap show .vmdk files from Veeam possibly but I definitely didn't select them, and the VM settings are just showing the main two .vmdk files.
Can anyone shed any light as to why the Exchange VM has reverted back to 30/08/2015 as I'm now pretty worried about this happening again in the future
From what you describe, it looks like the VM is/was running with active snapshots, and when you re-attached the main .vmdk files, you used an old state. With snapshots in place you always need to use the latest snapshot in the chain to have the recent data. Since a snapshot cannot be added to a VM from the GUI, you need to edit the VM's configuration file from the command line, and reload the .vmx file after this.
Btw. I assume that you know that the G6 model is not supported for ESXi 6.0, and that you should consider to use at least Update 1a (see http://kb.vmware.com/kb/2124669).