Intel 170 Servers, AS/400 RISC Server, 7xx Servers manual Virtual Scsi Bandwidth-Disk Scaling

14.6.2.4 Virtual SCSI Bandwidth-Disk Scaling

Figure 4 shows a comparison of measured bandwidth while scaling disk drives with varying block sizes of operations. Each of the network storage descriptions have a single network storage space attached to them. The difference in the scaling of these tests is attributable to the performance gain which can be achieved by adding disk drives and IO adapters. The figures below include small (4k-64k) transactions and larger (128k) transactions.

Read Performance-Small Transactions

Write Performance-Small Transactions

300
250
200
150
100
50
0
15 Disk	30 Disk	45 Disk
	D isk

1 NWSD

2 NWSD

4 NWSD

8 NWSD

16 NWSD 24 NWSD

250
200
150
100
50
0
15 Disk	30 Disk	45 Disk

D isk

1 NWSD

2 NWSD

4 NWSD

8 NWSD

16 NWSD 24 NWSD

Read Performance - Large

Transactions

Write Performance-Large Transactions

600
400
200
0
15 Disk	30 Disk	45 Disk
	D isk

1 NWSD

2 NWSD

4 NWSD

8 NWSD

16 NWSD 24 NWSD

300
250
200
150
100
50
0
15 Disk	30 Disk	45 Disk
	D isk

1 NWSD

2 NWSD

4 NWSD

8 NWSD

16 NWSD 24 NWSD

Figure 4 The figures above show read and write performance for small (4k-64k) and large transactions (128k+). This experiment shows that adding disk drives increases the throughput. A system with 45 disk drives will be able to transfer approximately 3 times faster then a system with 15 disk drives. Notice 24-network storage descriptions were used in order to achieve maximum performance.

IBM i 6.1 Performance Capabilities Reference - January/April/October 2008
© Copyright IBM Corp. 2008	Chapter 14 DASD Performance	237