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For VIOS attachment (NPIV-attachment), the Fibre Channel adapter queue depth is a storage performance-related tunable parameter. It can be considered to be increased if not already using VIOS version 2.2.4.10 or later and having deployed its default rule set  for applying IBM recommended device settings. 

The Fibre Channel adapter model-dependent current setting for its adapter queue depth, its allowed range, and its increase to its maximum supported value is shown in Example 6-4. With the fcs X  FC adapter port resource usually in use, as implied in the example, VIOS would still need to be restarted for the permanent change of the adapter queue depth that is made to its resource database to become effective. 

$ lsdev -dev fcs0 -attr | grep num_cmd_elems num_cmd_elems 500 Maximum number of COMMANDS to queue to the adapter True $ lsdev -dev fcs0 -range num_cmd_elems 20...4096 (+1) $ chdev -dev fcs0 -perm -attr num_cmd_elems=4096 fcs0 changed 

For both native and VIOS NPIV-attachment, the IBM FlashSystem 900 LUNs report to IBM i as device type D840 disk units, as shown in Figure 6-7 on page 165. 

Figure 6-7 shows the disk configuration of a newly set up IBM i partition with its load source unit, that is, disk unit 1 being the only disk unit configured in the system ASP (ASP 1). All disk units are accessible from IBM i through two active Fibre Channel paths. The IBM i integrated multi-path driver distributes the I/O across all active paths of a disk unit using a round-robin algorithm with some load-balancing applied. Non-configured and non-initialized disk units, that is, those not assigned to an IBM i ASP yet, are still reported with DPH xxx  resource names. 

