You might think that taking a snapshot of a virtual machine before you make any changes to it is a life saver as an IT pro, but I can assure you they are not.
Take a step back and think about what you are doing….you are taking a snapshot of a running server during its normal running operations so that you can roll back quickly if the shit hits the fan. It’s a running server…what about transaction which may or may not have been written to disk if its a SQL or Exchange server?
Yeah but it snapshots the VM’s memory as well you say? well guess what, between taking a snapshot of the memory and the disk, there could still be transaction between the two or on the network. Either way you’ve just increased the risk profile of you being able to successfully restore the VM to a consistent state after its just screwed the pooch.
So smarty pants, what should I do?
Don’t get me wrong, snapshots are great but shut the VM down and then take a snapshot. This way you have a consistent state on the VM so you can roll back quickly. If shutting down the VM is not an option, then stop all services which may be processing transactions.