While using VMware’s Update Manager to upgrade a 4.0 ESX host to vSphere 5, I ran into a space issue. Looking at the event tab on the ESX host in question, the error stated that at least 297 MB free space was required for the upgrade.
A quick putty session to verify the actual free space on the host and I noticed the following suspicious esx3 folders taking up a considerable amount of space. These folders were remnants left over from the ESX3 to 4 upgrade. The folders were there to allow for a roll back. They were never cleaned out and were preventing my upgrade now.
Fortunately, VMware has a nifty little command called cleanup-esx3 which when run will clear out these unnecessary files. Once removed, you can no longer roll back to ESX3. Most likely not an issue.
After a quick reboot, the folders and mount points are removed from the system.
You can also remove the folders manually. Once the necessary space was freed up, rerunning the Update Manager task did it’s thing.