VM snapshots are one of the best virtualization features ever. But…have you ever had a VMware vSphere or Hyper-V snapshot grow out of control and fill the datastore the VM resides on? You know what happens… even the best VM admins out there seem to get burned once when they create a snapshot for some routine maintenance and just forget about it afterwards. All VMs on that LUN crash and go into a suspended state until free space is added to the datastore.
Sometimes this task is harder than it sounds. If your SAN is out of space, or the SAN management tools are out of your control, you could be stuck.
But… follow a simple trick to give yourself that last little bit of wiggle room in the event that a snapshot fills a datastore.
Add a large text file to the root of the datastore that you can delete if you need headroom! I know it sounds too simple… but it’s simple and effective.
These directions are updated for VMware 6.5 environments, and work all the way back through vSphere 5.5, but the same concept applies to any hypervisor out there today.
If you’re on a SAN that performs some sort of data savings, through either compression and/or deduplication, this trick also consumes next to no space on the SAN.
How do you do this?
Enable the SSH server, and remote into one of the ESXi hosts. This example is from a vSphere 5.5 ESXi server from my home lab.
Change directories into the root of the datastore that you want to create the file in.
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