Chapter 2. IBM eX5 technology 41
controller makes decisions to move virtual servers between physical hosts to cater to each
guest OS resource requirement and, when possible, shuts down unneeded physical hosts to
save power.
Aggressive power management at the hardware level can interfere with the OS-level power
management, resulting in a common occurrence where virtual servers move back and forth
across the same set of physical host servers. This situation results in an inefficient
virtualization environment that responds slowly and consumes more power than necessary.
Running the server in Performance Mode prevents this occurrence, in most cases.
Custom Mode
The default value that is set in new eX5 systems is Custom Mode, as shown in Figure 2-23. It
is the recommended factory default setting. The values are set to provide optimal
performance with reasonable power consumption. However, this mode allows the user to
individually set the power-related and performance-related options.
See 2.7.3, “Performance-related individual system settings” on page 43 for a description of
individual settings.
Figure 2-23 Custom Mode factory default values
Table 2-5 shows comparisons of the available operating modes of IBM eX5 servers. Using the
Custom Mode, it is possible to run the system using properties that are in-between the
predetermined operating modes.
Table 2-5 Operating modes comparison
Settings Efficiency Acoustics Performance Custom (Default)
Memory Speed Power Efficiency Minimal Power Max Performance Max Performance
CKE Low Power Enabled Enabled Disabled Disable
Proc Performance States Enabled Enabled Enabled Enable
C1 Enhanced Mode Enabled Enabled Disabled Enable
CPU C-States Enabled Enabled Disabled Enable
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