HP XP20000XP24000 Disk Array - Manual (Page 11)

1 About LUSE Operations
Overview of HP StorageWorks XP LUN Expansion (LUSE)
LUN Expansion (LUSE) operations allow hosts that can use only a limited amount of LUs per fibre interface
to have access to larger amounts of data by using expanded LUs.
LUSE Function
LUN Expansion (LUSE) is a function for open systems. To use this function, you need the software called
Open Volume Management.
The LUSE function is applied to open-system logical volumes and enables you to configure one large
logical volume by combining several small LDEVs. The LUSE function allows hosts that can use only a
limited number of logical units (LUs) per fibre interface to have access to larger amounts of data by
using expanded LUs.
Figure 1 on page 11 shows the LUSE configuration. By using the LUSE function, you can combine several
logical devices (LDEVs) or volumes into one large logical volume. The size of the configured LDEV can be
expanded up to 36 times the size of the original LDEV. The ID of the logical volume defined as the large
logical volume is represented by the smallest LDEV ID (assigned to the top LDEV). The host recognizes
the expanded logical volume as one representative LDEV. As long as the number of LDEVs combined
into one large logical volume does not exceed the specified limit (see Table 2 on page 12), you can
arbitrarily select any LDEVs as the volumes to combine, regardless of their size (or capacity) or whether
or not they are on the same CU (Control Unit). The LUSE function also allows you to combine several
LDEVs and a LUSE volume (combined LDEVs) into one LUSE volume or combine LUSE volumes together
into one LUSE volume.
Before the host can access each LDEV composing an expanded LU (LUSE volume), you must release
the expanded LU.
LDEV (1:00)
LUSE (1:00)
The host sees LUSE
volumes as one LDEV. LDEV (1:01)
Host
LDEV (1:03)
LUSE (1:04)
LDEV (1:04)
LDEV (1:05)
Figure 1 LUSE Configuration
To create an open-systems volume (LU) larger than 2.8 TB, you must use LUSE to combine open-systems
volumes so that a LUSE volume larger than 2.8 TB is created.
XP24000 LUN Expansion User's Guide 11