Iv5R2 Direct Attach Dasd - IBM 170 Servers Manual

14.1.2 iV5R2 Direct Attach DASD

This section discusses the direct attach DASD subsystem performance improvements that were
new with the iV5R2 release. These consist of the following new hardware and software
offerings :
2757 SCSI PCI RAID Disk Unit Controller (IOA)
2780 SCSI PCI RAID Disk Unit Controller (IOA)
2844 PCI Node I/O Processor (IOP)
4326 35 GB 15K RPM DASD
4327 70 GB 15K RPM DASD
Note: for more information on the older IOAs and IOPs listed here see a previous copy of the
Performance Capabilities Reference.
14.1.2.1
I/O Intensive Workload Performance Comparison
2778/6718 5074 tower 18GB 10K rpm
2757/6718 5074 tower 18GB 10K rpm
2778/6719 5074 tower 35GB 10K rpm
2757/6719 5074 tower 35GB 10K rpm
2757/6719 5094 tower 35GB 10K rpm
0.35
0.3
0.25
0.2
0.15
0.1
0.05
0
0 1000
For our workload we attempt to fill the DASD units to between 40 and 50% full so you are
comparing units with more actual data, but trying to keep the relative seek distances similar. The
reason is that larger capacity drives can appear to be faster than lower capacity drives in the
same environment running the same workload in the same size database. That perceived
improvement can disappear, or even reverse depending upon the workload (primarily because of
where on the disks the data is physically located).
IBM i 6.1 Performance Capabilities Reference - January/April/October 2008
©
Copyright IBM Corp. 2008
Compare 2778/2757 & 5074 vs 5094
2757/4326 5094 tower 35GB 15K rpm
2757/4327 5094 tower 70GB 15K rpm
2757/4328 5094 tower 140GB 15K rpm
40% DASD Subsystem Utilization
2000 3000 4000
Workload Throughput
Chapter 14 DASD Performance
5000 6000 7000
192