Intel 170 Servers, AS/400 RISC Server manual Direct Attach 571E/574F and 571F/575B Observations

14.1.10 Direct Attach 571E/574F and 571F/575B Observations

We did some simple comparison measurements to provide graphical examples for customers to observe characteristics of new hardware. We collected performance data using Collection Services and Performance Explorer to create our graphs after running our DASD IO workload (small block reads and writes).

IOP vs IOPLess: no measurable difference in CPU or throughput.

Newer models of DASD are U320 capable and with the new IOAs can improve workload throughput with the same number of DASD or even less in some workload situations.

IOA’s 571E/574F and the 571F/575B achieved up to 25% better throughput at the 40% DASD Subsystem Utilization point than the 2780/574F IOA. The 571E/574F and 2780/574F were measured with 15 DASD units in a 5094 enclosure. The 571F/575B IOAs attached to #5786 EXP24 Disk Drawers.

System Models and Enclosures: Although an enclosure supports the new DASD or new IOA, you must ensure the system is configured optimally to achieve the increased performance documented above. This is because some card slots or backplanes may only support the PCI protocol versus the PCI-X protocol. Your performance can vary significantly from our documentation depending upon device placement. For more information on card placement rules see the following link:

IBM i operating system iV5R2: http://www.redbooks.ibm.com/redpapers/pdfs/redp3638.pdf IBM i operating system iV5R3, iV5R4: http://www.redbooks.ibm.com/redpapers/pdfs/redp4011.pdf

Conclusions: There can be great benefits in updating to new hardware depending upon the system workload. Most DASD intense workloads should benefit from the new IOAs available. Large block operations will greatly benefit from the 5094/5294 feature code #6417/9517 enclosures in combination with the new IOA’s and DASD units.

Note: The #6417/9517 provides a faster HSL-2 interface compared to the #2887/9877 and is available for I/O attached to POWER-5 based systems

IBM i 6.1 Performance Capabilities Reference - January/April/October 2008
© Copyright IBM Corp. 2008	Chapter 14 DASD Performance	204