Just to be clear, the VAAI delete maps to the SCSI UNMAP command, the SCSI equivalent of TRIM for SATA devices, and its support is disabled by default in ESXi regardless of the storage target. The VMware recommendation is to keep it disabled (can cause performance issues when unmapping blocks in real-time as files are deleted), and instead schedule it to run occasionally during low-usage time. To do a manual/batch unmap of all unused blocks on a datastore, use this command (ESXi 5.5 - it was different before but I don't have the old command handy right now): 'esxcli storage vmfs unmap -l <datastore-name>' either from the console of a host (local console or SSH shell), or remotely from anywhere with the 'esxcli' tool (its in the SDK downloads somewhere) and add a parameter like this: 'esxcli --server <hostname> storage vmfs....'FWIW LIO supports VAAI (Delete is disabled by default) over iSCSI. At least in Ubuntu 14.04.1+ . Good support for IB as well.