HP XP Racks - Manual (Page 20)

What is HDLM?
The widespread use of data warehousing and increasing use of multimedia
data have increased the need for high-speed processing of large volumes of
data on networks. To satisfy this need, networks dedicated to data transfer,
such as a SAN, are now being used to provide access to storage systems.
The HDLM software manages access paths to storage systems. HDLM uses
MPIO functionality supported by AIX 5L V5.2 or later.
HDLM, as an extended module of MPIO, provides functionality for distributing
the load across paths and switching to another path if there is a failure in a
path being used, thus improving system availability and reliability.
The figure below shows the connections between hosts and storage systems.
A server on which HDLM is installed is called a host.
Figure 1-1 Connections between hosts and storage systems
For details about the storage systems supported by HDLM, see Storage
Systems Supported by HDLM on page 3-6 .
HDLM Features
HDLM features include the following:
The ability to distribute a load across multiple paths. This is also known as
load balancing.
When a host is connected to a storage system via multiple paths, HDLM
can distribute the load across all the paths. This prevents one, loaded
down path from affecting the processing speed of the entire system.
For details on load balancing, see
Distributing a Load Using Load
Balancing on page 2-8 .
1-2
Overview of HDLM
Hitachi Dynamic Link Manager (for AIX) User Guide