HP StorageWorks XP Remote Web Console Software - Manual (Page 15)

LUN Configuration and Security Manager XP user guide for the XP128/XP1024 15
In Figure 1 , the LUs associated with the hg-lnx domain are addressed by numbers 0 to 2. The address
number of an LU is referred to as the logical unit number (LUN). When HP StorageWorks Continuous
Access XP and other optional features manipulate LUs, they use LUNs to specify the LUs to be manipulated.
You can add, change, and delete LU paths when the system is operational. For example, if new disks or
server hosts are added to your disk array, you can add new LU paths. If an existing server host is to be
replaced, you can delete the corresponding LU paths before replacing the host. You do not need to restart
the system when you add, change, and delete LU paths.
If a hardware failure (such as a CHA failure) occurs, there is a chance that some LU paths are disabled
and some I/O operations are stopped. To avoid this, the system administrator can define alternate LU
paths. If one LU path fails, the alternate path takes over the host I/O.
In a Fibre Channel environment, up to 1,024 LU paths can be defined for one host storage domain. Up to
1,024 LU paths can be defined for one port.
NOTE: You cannot define an LU path to LUN On Demand volumes or volumes reserved by Auto LUN XP.
• Up to 256 host storage domains can be created for one Fibre Channel port. Up to 57,344 host storage
domains can be created for one disk subsystem. The maximum number of ports per subsystem is 224.
• Up to 255 host groups can be created for one Fibre Channel port.
Configuring LU paths in a NAS environment
In a Fibre Channel or iSCSI environment, hosts are classified into platform-based host groups (host storage
domains). This is not required in a NAS environment. Hosts attached to a NAS port are registered
automatically in a host group (host storage domain) called User.
In a NAS environment, LUs are classified into system LUs and user LUs. System LUs contain system
information necessary for managing the NAS environment and can only be manipulated by your HP
account support representative. User LUs contain data that can be accessed by ordinary network users.
When configuring a NAS system, you need to define paths between hosts and user LUs.
Figure 2 shows an example of defined paths between hosts and user LUs. In a NAS environment, paths are
always defined between a user LU and a group of four ports. In Figure 2 , two paths are defined to the user