YES!
I deleted partition 3 and then could increase the datastore with the missing 1.8TB using vSphere Client 5.5.0-3024345.
This is the result:
/vmfs/volumes # df -h
Filesystem Size Used Available Use% Mounted on
VMFS-5 5.5T 2.1T 3.4T 38% /vmfs/volumes/mainstorage
vfat 249.7M 185.2M 64.5M 74% /vmfs/volumes/aeda2aeb-c934ad60-46ce-cb77abdfabaa
vfat 249.7M 182.4M 67.4M 73% /vmfs/volumes/c8ace7e9-a96a5914-16d4-a697ad4634d9
vfat 285.8M 201.6M 84.2M 71% /vmfs/volumes/55d7af6e-a25f7c97-c3ec-6805ca0de93c
I cannot explain how the partition got lost, but I read about vSphere C# Client having an issue with partitions >4TB.
Obviously this is solved with the current version. I upgraded to 5.5-U3 in the meantime.
Thank you very much!
