HP StorageWorks XP48 Disk Array - Manual (Page 22)

Overview of HP StorageWorks XP Provisioning Manager 22
Manager (HDLM). You must install HDLM on each host in advance. Figure 1-6 provides an overview of the
relationships between HDLM, the host, the storage subsystem, and the management servers when path
redundancy is provided.
HDLM manages access paths from a host port to a port in the storage subsystem. Because HDLM provides
functionality for switching to another path in the event of a failure and for distributing the workload among the
paths, linking HDLM with Provisioning Manager provides the following advantages:
• Failover
You can set up multiple paths between the host and logical units (LUs) in the subsystem. If a failure
occurs on an active path, HDLM automatically switches to another normal path so that processing can
continue.
• Failback
When a failed path is recovered, HDLM can restore the recovered path to active status (the status in
which I/Os can be issued normally).
• Load distribution
You can set up multiple paths between the host and the LUs in the subsystem. Appropriate paths are
used for I/O processing at the LUs. This prevents performance in the overall system from being degraded
due to the workload being concentrated on a particular path.
• Path health check
HDLM can automatically check the status of paths at regular intervals and is able to detect failures. This
enables the user to recognize path errors and take appropriate action.
For more information on Dynamic Link Manager, please see the following documents:
• Hitachi Dynamic Link Manager User’s Guide for AIX® Subsystems
• Hitachi Dynamic Link Manager User’s Guide for Sun™ Solaris™ Subsystems