144 IBM eX5 Implementation Guide
These options are configured by using the UEFI during the boot sequence.
4.8.8 Effect on performance of using mirroring or sparing
To understand the effect on performance of selecting various memory modes, we use a
system configured with X7560 processors and populated with sixty-four 4 GB quad-rank
DIMMs.
Figure 4-19 shows the peak system-level memory throughput for various memory modes
measured using an IBM-internal memory load generation tool. As shown, there is a 50%
decrease in peak memory throughput when going from a normal (non-mirrored) configuration
to a mirrored memory configuration.
Figure 4-19 Relative memory throughput by memory mode
62
50
100
Sparing
Mirroring
Normal
Relative Memory Throughput by Memory Mode
Relative Memory Throughput
0 20 40 60 80 100 120