Performance Tuning
Assigned CMs
A controller that controls access is assigned to each RAID group and manages the load balance in the ETERNUS
DX. The controller that controls a RAID group is called an assigned CM.
Figure 61
Assigned CMs
ETERNUS DX
Switch
CM#1
RAID group #1
RAID group #0
Switch
RAID group #2
CM#0
Assigned
CM
The assigned CM of the RAID
group controls access
Assigned
CM
If specific controllers have a load bias, change the assigned CM to equalize the load.
If an assigned controller is disconnected for any reason, the assigned CM is replaced by another controller. After
the disconnected controller is installed again and returns to normal status, this controller becomes the assigned
CM again.
●
Auto Assignment of Assigned CMs
This section describes the selection criteria if auto assignment is selected for an assigned CM when RAID
groups are created. It is also possible to manually change the assigned CM.
The assigned CM is determined by the value when the RAID group number is divided by the number of
controllers. If a CM exists that is not installed or is malfunctioning, the assigned CM is allocated such that
the load is evenly distributed across the CMs that are running normally.
The following table shows the assigned CM when all CMs are installed and are running normally.
Table 52
Auto Assignment of Assigned CMs (for 2 CMs)
The value when the RAID group number is divided by the
number of controllers
Assigned CMs (auto assignment)
Even number
CE#0 CM#0
Odd number
CE#0 CM#1
Table 53
Auto Assignment of Assigned CMs (for 4 CMs)
The remainder when the RAID group number is divided by the
number of controllers
Number of CMs (number of CEs)
2 (1CE)
4 (2CE)
0
CE#0 CM#0
CE#0 CM#0
2. Basic Functions
Performance Tuning
121
Design Guide
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