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VMware KB: Growing or expanding a VMFS volume or datastore
open a 2nd Vsphere and connect to an esx host (via IP or Hostname.)
go to config tab - storage adapters and perform a rescan
go to config tab - storage, right click on volume.
ensure that new size of device is listed on the Extent Device List (bottom right pane) - your SAN Device
click "increase"
Select the correct storage device (your SAN Device)
hit next a few times (checking settings as you go) your Volume increase on your SAN will be reflected on your VSphere Client.