Further Notes About Ixs/Ixa Disk Operations - IBM 170 Servers Manual

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iSCSI IXS/IXA w Caching Disabled or Shared
The charts shows the relative cost when performing 5 different types of operations
Random write operations of a uniform size (512, 1k, ... 64k).
Random read operations of a uniform size (512, 1k, ... 64k).
A 35% random write, 65% random read mix of operations with a uniform size (termed transaction
processing type load).
A fileserving type load - which consists of a mix of operations of various sizes similar in ratio to
typical fileserving loads. This load is 80% random reads.
An application server - database type load. This is also a mix to simulate the character of application
and database type accesses - mostly random with about 40% reads.

17.4.1 Further notes about IXS/IXA Disk Operations

Maximum disk operation size supported by the IXS or IXA is 32k. Thus, any Windows disk
operations greater than 32k will result in the Windows operating system splitting the operation into 2
or more sequential operations.
The IXS/IXA cost calculation is slightly greater on a POWER5® system (System i5) than on earlier
8xx systems. This includes some increased overhead costs in V5R4, and the new processor types. Use
the newer rules of thumb listed above for CPW calculations.
It does not matter if a storage space is linked statically or dynamically, the performance
characteristics are identical.
It does not matter if a server is an IXS or an IXA attached System x server, the disk performance is
almost identical.
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Measured on a System i Model 570 - 2-way 26F2 processor (7495 capacity card), rated at 6350 CPWs, V5R4
release of i5/OS, 40 parity protected (RAID 5) 4326 disks, 3 2780 disk controllers. The IXA attached server was
a x365xSeries (4way 2.5Ghz Xeon with IXA and Windows Server 2003 with SP1. The iSCSI servers were HS20
BladeCenter servers with a copper iSCSI (p/n 26K6489) daughter card. Switches were Nortel L2/3 Ethernet (p/n
26K6524) and Cisco Intelligent Gigabit Switch (p/n )
IBM i 6.1 Performance Capabilities Reference - January/April/October 2008
©
Copyright IBM Corp. 2008
CPW per 1k Disk Operations
Chapter 17 - Integrated BladeCenter and System x Performance
IXS/IXA w Caching Enabled
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