IBM 170 Servers Manual page 200

In comparing Mirroring and RAID one of the concerns is capacity differences and the hardware
needed. We tried to create an environment where the capacity was the same in both
environments. To do this we built the same size database on "15 35GB DASD using RAID5"
and "14 70GB DASD using Mirroring spread across 2 IOAs". The protection in the Mirrored
environment is better but it also has the cost of an extra IOA in this low number DASD
environment. For the 30 DASD and 60 DASD environments the number of IOAs needed is
equal.
14.1.7.3
0.25
0.15
0.05
14.1.7.4
40
30
20
10
IBM i 6.1 Performance Capabilities Reference - January/April/October 2008
©
Copyright IBM Corp. 2008
RAID-5 compared to Mirroring
571E/574F (15 - 35 GB DASD): IOPLess, RAID-5
571E (14 - 70 GB DASD): IOPLess, 7 Mirrored Pairs 2 IOAs
571E (30 DASD): IOPLess, 15 Mirrored Pairs 2 IOAs
571E/574F (30 DASD): IOPLess, RAID-5 2 IOAs
571E (60 DASD): IOPLess, 30 Mirrored Pairs 4 IOAs
571E/574F (60 DASD): IOPLess, RAID-5 4 IOAs
0.2
0.1
0
0 5000 10000 15000 20000 25000 30000 35000 40000
RAID-5 compared to Mirroring
571E/574F (15 - 35 GB DASD): IOPLess, RAID-5
571E (14 - 70 GB DASD): IOPLess, 7 Mirrored Pairs 2 IOAs
571E (30 DASD): IOPLess, 15 Mirrored Pairs 2 IOAs
571E/574F (30 DASD): IOPLess, RAID-5 2 IOAs
571E (60 DASD): IOPLess, 30 Mirrored Pairs 4 IOAs
571E/574F (60 DASD): IOPLess, RAID-5 4 IOAs
0
0 2000
Chapter 14 DASD Performance
Workload Throughput
4000 6000
Ops/Sec
8000 10000
200