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306 DS6000 Series: Concepts and Architecture
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Path# Adapter/Hard Disk State Mode Select Errors
0 fscsi2/hdisk17 OPEN NORMAL 0 0
1 fscsi2/hdisk19 OPEN NORMAL 27134 0
2 fscsi3/hdisk21 OPEN NORMAL 0 0
3 fscsi3/hdisk23 OPEN NORMAL 27352 0
DEV#: 1 DEVICE NAME: vpath4 TYPE: 1750 POLICY: Optimized
SERIAL: 20522873
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Path# Adapter/Hard Disk State Mode Select Errors
0 fscsi2/hdisk18 CLOSE NORMAL 25734 0
1 fscsi2/hdisk20 CLOSE NORMAL 0 0
2 fscsi3/hdisk22 CLOSE NORMAL 25500 0
3 fscsi3/hdisk24 CLOSE NORMAL 0 0
This lsvpcfg command helps verify the vpath configuration state. See Example A-7.
Example: A-7 lsvpcfg command
vpath0 (Available pv) 018FA067 = hdisk1 (Available) hdisk3 (Available) hdisk5 (Available)
vpath1 (Available ) 019FA067 = hdisk2 (Available) hdisk4 (Available) hdisk6 (Available)
The hd2vp command converts a volume group made of hdisk devices to an SDD vpath device
volume group. Run
hd2vp <volumegroup name> for each volume group to convert.
Multipath I/O (MPIO)
AIX MPIO is an enhancement to the base OS environment that provides native support for
multi-path Fibre Channel storage attachment. MPIO automatically discovers, configures, and
makes available every storage device path. The storage device paths are managed to
provide high availability and load balancing of storage I/O. MPIO is part of the base kernel
and is available for AIX 5.2 and AIX 5.3.
The base functionality of MPIO is limited. It provides an interface for vendor-specific
Path
Control Modules
(PCMs) which allow for implementation of advanced algorithms.
IBM provides a PCM for DS6000 that enhances MPIO with all the features of the original
SDD. It is called SDDPCM and is available from the SDD download site (refer to 14.2,
“Subsystem Device Driver” on page 280).
There are some reasons to prefer MPIO (with SDDPCM) to traditional SDD:
Performance improvements due to direct integration with AIX
Better integration if different storage systems are attached
Easier administration through native AIX commands
For basic information about MPIO see the “Multiple Path I/O” section in the
AIX 5L System
Management Concepts: Operating System and Devices
guide:
http://publib16.boulder.ibm.com/pseries/en_US/aixbman/admnconc/hotplug_mgmt.htm#mpioconcepts
Important: If you choose to use MPIO with SDDPCM instead of SDD, you have to remove
the regular DS6000 Host Attachment Script and install the MPIO version of it. This script
identifies the DS6000 volumes to the operating system as MPIO manageable. Of course,
you can’t have SDD and MPIO with SDDPCM on a given server at the same time.