HP 3PAR VMware ESX Implementation Guide

Target Port Limits and Specifications
To avoid overwhelming a target port and ensure continuous I/O operations, observe the following
limitations on a target port:
• For information available on host port per target port and the maximum total host ports per
array, see the HP 3PAR Feature Availability Matrix documentation on the HP Single Point of
Connectivity Knowledge (HP SPOCK) website: HP SPOCK
• I/O queue depth on each HP 3PAR StoreServ Storage HBA model, as follows:
◦ QLogic CNA: 1748 (HP 3PAR StoreServ 10000 and HP 3PAR StoreServ 7000 systems
only)
• I/O queues are shared among the connected host HBA ports on a first-come, first-served basis.
• When all queues are in use and a host HBA port tries to initiate I/O, it receives a target queue
full response from the HP 3PAR StoreServ Storage port. This condition can result in erratic I/O
performance on each host. If this condition occurs, each host should be throttled so that it
cannot overrun the HP 3PAR StoreServ Storage port's queues when all hosts are delivering
their maximum number of I/O requests.
NOTE: When host ports can access multiple targets on fabric zones, the assigned target number
assigned by the host driver for each discovered target can change when the host is booted and
some targets are not present in the zone. This situation may change the device node access point
for devices during a host reboot. This issue can occur with any fabric-connected storage, and is
not specific to the HP 3PAR StoreServ Storage.
HP 3PAR Priority Optimization for FCoE
The HP 3PAR Priority Optimization feature introduced in HP 3PAR OS 3.1.2.MU2 is an efficient
and dynamic solution for managing server workloads and can be utilized as an alternative to
setting host I/O throttles. Using this feature, a storage administrator can share storage resources
effectively by enforcing quality of service limits on the array. No special settings are needed on
the host side to obtain the benefit of HP 3PAR Priority Optimization although certain per target or
per adapter throttle settings may need to be adjusted. For complete details of how to use HP 3PAR
Priority Optimization (Quality of Service) on HP 3PAR StoreServ Storage arrays, see the HP 3PAR
Priority Optimization technical whitepaper (HP document #4AA4-7604ENW), on the HP website:
HP 3PAR Priority Optimization
HP 3PAR OS Persistent Ports for FCoE
The HP 3PAR OS Persistent Ports (or virtual ports) feature minimizes I/O disruption during an
HP 3PAR StoreServ Storage online upgrade or node-down event (online upgrade, node reboot,
or cable pull test). Port shutdown or reset events do not trigger this feature.
Each FCoE target storage array port has a partner array port automatically assigned by the system.
Partner ports are assigned across array node pairs.
HP 3PAR OS Persistent Ports allows an HP 3PAR StoreServ Storage FCoE port to assume the identity
of a failed port while retaining its own identity. Where a given physical port assumes the identity
of its partner port, the assumed port is designated as a persistent port. Array port failover and
failback with HP 3PAR OS Persistent Ports is transparent to most host-based multipathing software,
which can keep all of its I/O paths active.
NOTE: Use of HP 3PAR OS Persistent Ports technology does not negate the need for properly
installed, configured, and maintained host multipathing software.
Target Port Limits and Specifications 35