HP Hitachi Dynamic Link Manager Software - Manual (Page 38)

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
function is used. Both figures show examples of I/O operations being issued
for the same LU by multiple applications.
Figure 2-7 Flow of I/O Data When the Load Balancing Function Is Not
Used
When the load balancing function is not used, I/O operations converge onto a
single path (A). The load on that one path (A) will cause a bottleneck, which
might cause problems with system performance.
2-14
HDLM Functions
Hitachi Dynamic Link Manager User Guide for Linux ®