Chapter 14. DASD Performance
This chapter discusses DASD subsystems available for the System i platform.
There are two separate considerations. Before IBM i operating system V6R1, one only had to
consider particular devices, IOAs, IOPs, and SAN devices. All attached through similar
strategies directly to IBM i operating system and were all supported natively.
Starting in IBM iV6R1, however, IBM i operating system will be permitted to become a virtual
client of an IBM product known as VIOS. The supported BladeCenter products like the JS12
Express and JS22 Express will only be available in this fashion. For other IBM Power Systems
it will be possible to attach all or some of the disks in this manner. This product and its
implications will be discussed commencing with section 14.5.
14.1 Internal (Native) Attachment.
This section is intended to show relative performance differences in Disk Controllers which I
will refer to as IOAs, DASD and IOPs, for customers to compare some of the available
hardware. The workload used for our throughput measurements should not be used to gauge the
workload capabilities of your system, since it is not a customer like workload.
The workload is designed to concentrate more on DASD, IOAs and IOPs, not the system as a
whole. Workload throughput is not a measurement of operations per second but an activity
counter in the workload itself. No LPAR’s were used, all system resources were dedicated to the
testing. The workload is batch and I/O intensive (small block reads and writes).
This chapter refers to disk drives and disk controllers (IOAs) using their CCIN number/code.
The CCIN is what the system uses to understand what components are installed and is unique by
each device. It is a four character, alphanumeric code. When you use commands in IBM i
operating system to print your system configuration like PRTSYSINF or use the WRKHDWRSC
*STG command to display hardware configuration information for your storage devices like the
571E or 571F disk controllers you see a listing of CCIN codes.
Note that the feature codes used in IBM's ordering system, e-config tool and inventory records
are a four character numeric code which may or may not match the CCIN. IBM will sometimes
use different features for the exact same physical device in order to communicate how the
hardware is configured to the e-config tool or to provide packaging or pricing structures for the
disk drive or IOA. For example, feature code 5738 and 5777 both identify a 571E IOA. A
fairly complete list of CCIN and their feature codes can be found in an appendix of the System
Builder located near the end of the publication, and a partial list can be found on the following
page.
IBM i 6.1 Performance Capabilities Reference - January/April/October 2008
©
Copyright IBM Corp. 2008
Chapter 14 DASD Performance
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