IBM DS8000 manual Managing multiple paths, Subsystem device driver SDD, Useful SDD commands

Device	Specific.(ZB)	C2D3.91A1
Device	Specific.(YL)	U1.13-P1-I1/Q1

You can also print the WWPN of an HBA directly by running

lscfg -vl <fcs#> grep Network

The # stands for the instance of each FC HBA you want to query.

Managing multiple paths

It is a common and recommended practice to assign a DS8000 volume to the host system through more than one path, to ensure availability in case of a SAN component failure and to achieve higher I/O bandwidth. AIX will discover a separate hdisk for each path to a DS8000 logical volume.

To utilize the path redundancy and increased I/O bandwidth, you need an additional software layer in the AIX disk subsystem to recombine the multiple hdisks into one device.

Subsystem device driver (SDD)

The IBM Subsystem Device Driver (SDD) software is a host-resident pseudo device driver designed to support the multipath configuration environments in IBM products. SDD resides in the host system with the native disk device driver and manages redundant connections between the host server and the DS8000. SDD is available for AIX 5.1, 5.2, and 5.3.

Refer to 15.2, “Subsystem Device Driver” on page 324 for download information and installation and usage documentation.

Determine the installed SDD level

To determine whether SDD is installed, and at which level, you can use the lslpp -lcommand, as shown in Example A-5.

Example: A-5 lslpp -l “*sdd*”

FilesetLevel State Description

----------------------------------------------------------------------------

Path: /usr/lib/objrepos
devices.sdd.52.rte	1.5.1.2	COMMITTED	IBM Subsystem Device Driver
			for AIX V52
Path: /etc/objrepos
devices.sdd.52.rte	1.5.1.2	COMMITTED	IBM Subsystem Device Driver
			for AIX V52

Useful SDD commands

The datapath query device command displays information about all vpath devices. It is useful to determine the number of paths to each SDD vpath device and their status. See Example A-6.

Example: A-6 datapath query device command

{yli4642:root}/home/redbook -> datapath query device

Total Devices : 2

DEV#: 0 DEVICE NAME: vpath3 TYPE: 2107 POLICY: Optimized

SERIAL: 10522873

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Appendix A. Open systems operating systems specifics 349