HP Hitachi Dynamic Link Manager Software - Manual (Page 26)

1. Overview of HDLM
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1.2 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 2.6 Distributing a Load Using Load Balancing.
The ability to continue running operations between a host and storage system, even if
there is a failure. This is also known as performing a failover.
When a host is connected to a storage system via multiple paths, HDLM can
automatically switch to another path if there is some sort of failure in the path that
is currently being used. This allows operations to continue between a host and a
storage system.
For details on performing failovers, see 2.7 Performing Failovers and Failbacks
Using Path Switching.
The ability to bring a path that has recovered from an error back online. This is also
known as performing a failback.
If a path is recovered from an error, HDLM can bring that path back online. This
enables the maximum possible number of paths to always be available and online,
which in turn enables HDLM to better distribute the load across multiple paths.
Failbacks can be performed manually or automatically. In an automatic failback,
HDLM will automatically restore the path to an active state after the user has
corrected the problem that exists on the physical path.
For details on performing failbacks, see 2.7 Performing Failovers and Failbacks
Using Path Switching.
The ability to automatically check the status of any given path at regular intervals. This
is also known as path health checking.
HDLM can easily detect errors by checking the statuses of paths at user-defined
time intervals. This allows you to check for any existing path errors and to resolve
them promptly and efficiently.
For details on setting up and performing path health checking, see 2.9 Detecting
errors by using path health checking.