Distributing A Load Using Load Balancing - Hitachi XP P9500 User Manual

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 across
all, available paths, and some cannot. Therefore, even when the load
balancing function is used, a particular I/O operation might not necessarily
allocate data to every available path. RAID Manager issuing IOCTL to a
command device is an example of an I/O operation that cannot allocate data
to every path.
Figure 2-5 Flow of I/O Data When the Load Balancing Function Is Not Used on
page 2-7
not used.
Used on page 2-8
function is used. Both figures show examples of I/O operations being issued
for the same LU by multiple applications.
2-6
Figure 2-4 Positioning of HDLM Driver and NMP
shows the flow of I/O data when the load balancing function is
Figure 2-6 Flow of I/O Data When the Load Balancing Function Is
shows the flow of I/O data when the load balancing
HDLM Functions
Hitachi Dynamic Link Manager User Guide (for VMware(R))