I was trying to add an extent today for a lab I was doing and I couldn’t get the new disk to show up in the ‘increase’ wizard…
I knew that you had to make sure the new ‘extent’ disk was accessible on every ESXi host that was accessing the existing VMFS datastore. I check the storage controller and verified that it was. Turns out that all I had to do was do a ‘rescan’ on each host that had the existing VMFS datastore mapped on it. Once I did that, it showed up in the wizard. Until you do a rescan, the new disk was getting hidden by the ‘LUNs not exposed to all hosts that share the original VMFS datastore’ filter.