3PAR InForm® OS 2.2.4 Concepts Guide (320-200085 Rev B, March 2009)

9.2
VLUN Template Types
3PAR InForm OS Concepts Guide InForm OS Version 2.2.4
Once a VLUN template is applied to create one or more active VLUNs, hosts continue to be able
to access volumes based on the export rule established by that template. Removing VLUNs
associated with a volume halts host access to that volume. Removing all VLUNs for a host stops
the host from accessing all volumes.
9.2 VLUN Template Types
A VLUN template can be one of the following types:
■ Host sees allows only a specific host to see a volume.
■ Port presents allows any host on a specific port to see the volume.
■ Matched set allows only a specific host on a specific port to see the volume.
9.2.1 Host Sees
A host sees VLUN template allows only a particular host connected to any port to see a virtual
volume. The system makes the virtual volume visible as a LUN to all the host’s WWNs,
regardless of which controller node port the WWNs appear on. If the host has more than one
WWN, active VLUNs are created for each host WWN. However, for any single host, there can
only be one host sees VLUN template for a given LUN.
If a WWN is added to an existing host definition, all virtual volumes that are exported to the
host using the host-sees VLUN template are exported to the new WWN. However, WWNs
cannot be removed from a host definition if a LUN is exported to the host.
9.2.2 Port Presents
A port presents VLUN template allows any host connected to a particular port to see a virtual
volume. The system makes the virtual volume visible as a LUN to any of the host’s WWNs that
appear on the controller node port. As long as the VLUN template remains on the system,
additional active VLUNs are created when the port is attached to additional hosts. However,
there can only be one port presents VLUN template per port LUN combination.
The same virtual volume can be exported as different LUNs on the same or different ports.