The following error may occur if you have requested a VM to be deleted from disk :
A general system error occured: Input/output error
In my particular case, the VM was up to 12 Tb and after a little while the operation was running, the error message above showed up in vCenter.
The virtual machine was still present in the inventory, but the size consumed dropped down from 12 Tb to 64 Gb.
vCenter actually deleted all the vDisks (vmdk) but left the other files. Since that VM had 64 Gb of RAM, this is totally explained by the nvram file still present on the VM folder.
Just try to perform the “delete from disk” operation once more and the VM should be completely wiped out if you have no hardware/storage issue. This could have been explained by the latency on the storage at the time of this operation.