Dell PowerStore 3000T EMC PowerStore Host Configuration Guide - Page 37

Fibre Channel Configuration This section describes the recommended configuration that should be applied when attaching AIX hosts to PowerStore cluster using Fibre Channel. NOTE: When using Fibre Channel with PowerStore, the FC Host Bus Adapters (HBA) issues that are described in this section should be addressed for optimal performance. NOTE: In general, no more than eight(8) paths per LUN should be used with an AIX host that is connected to PowerStore. If more paths are needed, an RPQ is required. Pre-Requisites Before you install HBAs on an AIX host, the following pre-requisites should be met. Follow the IBM recommendations for installation and setup of the appropriate HBA for your system. It is recommended to install the latest driver version (patch), as described on the IBM support site for each specific FC HBA. Refer to the E-Lab Interoperability Navigator (https://elabnavigator.emc.com) for supported FC HBA models and drivers. Queue Depth Follow these recommendations when setting queue depth. NOTE: Changing queue depth settings is designed for advanced users. Increasing the queue depth may cause the host to overstress other clusters that are connected to the AIX host, resulting in performance degradation while communicating with them. Therefore, especially in mixed environments with multiple cluster types that are connected to the AIX host, compare the PowerStore recommendations for queue depth with those of other platforms before applying them. Queue depth is the number of SCSI commands (including I/O requests) that a storage device can handle at a given time. Queue depth can be set on either of the following levels: • Initiator level - HBA queue depth • LUN level - LUN queue depth LUN queue depth setting controls the amount of outstanding I/O requests per a single path. HBA queue depth (also referred to as execution throttle) setting controls the number of outstanding requests per HBA port. For optimal operation with PowerStore, it is recommended to adjust the HBA queue depth setting of the FC HBA. The driver module for the card controls LUN queue depth settings at the operating system level. Change the LUN queue depth default value (256) to a lower value only if I/O throttling is required. Setting the Queue Depth Follow these steps to set the HBA queue depth. About this task To set the HBA queue depth: Steps 1. Run the chdev command for each HBA in the AIX host to set the HBA firmware level queue depth: chdev -l fcs# -a num_cmd_elems=2048 -P 2. Reboot the AIX host to apply the HBA queue depth settings. Fast I/O Failure for Fibre Channel Devices This topic describes the Fast I/O Failure feature for FC devices and details the setting recommendations. AIX supports Fast I/O Failure for Fibre Channel devices after link events in a switched environment. Host Configuration for AIX 37