HP StorageWorks LUN Configuration and Security Manager XP user guide for the XP10000/XP12000 (December 2005)

LUN Configuration and Security Manager XP user guide for the XP10000/XP12000 37
2 Volume Management for the XP10000/XP12000
Use Volume Management to perform the following tasks:
• ”Volume Management (LU Size Expansion)” on page 37)
• ”Volume Size Configuration (VSC)” on page 38)
Volume Management (LU Size Expansion)
Volume Management (LU Size Expansion or LUSE) combines two or more LDEVs to function as a larger
LDEV. As a result, a host can access a greater amount of storage with a smaller number of LDEVs.
Figure 16 shows the effect of a LUSE configuration.
Figure 16 LUSE configuration
LUSE can combine up to 36 LDEVs into a LUSE volume. The LDEV number of the LUSE volume is the first or
lowest number of the LDEVs making up the LUSE volume. This is the top LDEV, and is the number the host
will recognize.
Drawbacks
• Some operating systems may experience slow disk access times with large logical units, if they contain
a large number of high-use files.
• The size of a LUSE volume can increase the amount of time required to perform backups.
LUSE rules
• Open volume emulation types OPEN-3, OPEN-8, OPEN-9, OPEN-E, OPEN-L, or OPEN-V are
supported.
• The maximum number of LDEVs that can be used to create a LUSE is 36.
• LDEVs must be of the same emulation type.
• LDEVs must be at the same RAID level. Combining RAID 1 and RAID 5 volumes into the same LUSE
volume is supported, but not recommended.
• LDEVs or LUSE volumes to be combined must have no assigned path definitions. These are known as
free (or available) LDEVs. For this reason, Business Copy, Continuous Access, TrueCopy (TC390),
ShadowImage (SI390), and Continuous Access XP - Journal pair volumes cannot be targets of LUSE
operations. For more information, see ”LUSE operations that handle a path-defined LDEV” on page 38.
• LDEVs that are to be combined into LUSE volumes must not be reserved for Auto LUN.