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14.6.4 AIX Virtual IO Client Performance Guide
The following is a link which will direct you to more in-depth performance tuning for AIX
virtual SCSI client.
Advanced POWER Virtualization on IBM p5 Servers: Architecture and Performance
Considerations http://www.redbooks.ibm.com/abstracts/sg247940.html?
14.6.5 Performance Observations and Tips
• In order to achieve best performance 1 network storage description should be used for
every 2-4 disks within an ASP.
• A method to improve write performance is to create 8 NWSD for every 15 disks.
• Best performance was obtained with a network storage description for every network
storage space.
• Sizing your memory correctly can improve read performance vastly.
• Multiple network storage descriptions (NWSD) can be attached to a single ASP. No
performance benefit from using multiple ASP’s was seen.
• For maximum logical volume throughput use multiple network storage spaces attached to
a single logical volume.
• With low I/O loads and a small number of partitions, Micro-Partitioning of the IBM i
operating system Server partition has little effect on performance.
• For a more efficient Virtual SCSI implementation with larger loads, it may be
advantageous to keep the I/O server as a dedicated processor.
• Extensive information can be found at the System i Information Center web site at:
http://publib.boulder.ibm.com/iseries.
14.6.6 Summary
Virtualization is an innovative technology that redefines the utilization and economics of
managing an on demand operating environment. POWER5 and future POWER architectures
provide new opportunities for clients to take advantage of virtualization capabilities. IBM i
operating system family provides the capability for a single physical I/O adapter to be used by
multiple logical partitions of the same server, enabling consolidation of I/O resources.
The system resource cost of Virtual SCSI implementation is small, and clients should assess the
benefits of the Virtual SCSI implementation for their environment. Simultaneous multithreading
should be enabled in a virtual SCSI environment.
Virtual SCSI implementation is an excellent solution for clients looking to consolidate I/O
resources with a modest amount of processor. The new IBM i operating system POWER
Systems Virtual SCSI capability creates new opportunities for consolidation, and demonstrates
strong performance and manageability.
IBM i 6.1 Performance Capabilities Reference - January/April/October 2008
© Copyright IBM Corp. 2008 Chapter 14 DASD Performance 242