HP XP P9500 Storage - Manual (Page 35)

Figure 2-6 About Alphabetic Letters Used in the Logical Device File Name
About numeric values used in a logical device file name:
[1-15] indicates a partition number in the applicable LU. For example, if
the logical device file name of an HDLM device is sddlmaa1, it indicates
partition 1 on sddlmaa. To specify the entire LU, simply use sddlmaa.
Note that HDLM creates block device files. The system dynamically selects
the major number of the block device that this file uses.
Distributing a Load Using Load Balancing
When the system contains multiple paths to a single LU, HDLM can distribute
the load across the paths by using multiple paths to transfer the I/O data.
This function is called load balancing, and it prevents a single, heavily loaded
path from affecting the performance of the entire system.
Note that some I/O operations managed by HDLM can be distributed to each
path, while others cannot. Therefore, even though load balancing function is
used, I/O operations might not be equally allocated to each path.
Figure 2-7 Flow of I/O Data When the Load Balancing Function Is Not Used on
page 2-14 shows the flow of I/O data when the load balancing function is
not used. Figure 2-8 Flow of I/O Data When the Load Balancing Function Is
Used on page 2-15 shows the flow of I/O data when the load balancing
HDLM Functions
2-13
Hitachi Dynamic Link Manager User Guide (for Linux(R))