HP StorageWorks XP Remote Web Console Software - Manual (Page 54)

54 Volume Management for the XP1024/XP128
• When you combine a LUSE volume with another LUSE volume, the range of LDEVs should not be
overlapped.
For example, if you combine LDEV00, LDEV03 and LDEV05 into LUSE 1, LDEV02 and LDEV04 into
LUSE 2, and LDEV06 and LDEV07 into LUSE 3, you can also combine LUSE 1 and LUSE 3. However,
you cannot combine LUSE 1 and LUSE 2, because the LDEV range in LUSE 1 and LUSE 2 is
overlapped.
• A maximum of 256 expanded logical units (LUs) can be configured on the same port.
• The maximum capacity of a LUSE volume is 2 TB for XP1024/XP128 arrays.
• The access attribute must be set to read/write when creating or releasing a LUSE volume.
• When releasing a LUSE volume, the volume should have no path definitions.
• Combining internal and external volumes is not supported.
• The IO suppression mode and cache mode settings of the LDEVs combined into a LUSE volume must
be the same.
• All the LDEVs combined into a LUSE volume must be of the same drive type (either the SATA drive or
non-SATA drive).
LUSE operations that handle a path-defined LDEV
You can use an LDEV or another LUSE volume that has path definitions as the top LDEV of the resulting
LUSE volume, and can combine the top LDEV with other LDEVs or LUSEs that have no path definitions.
Creating this type of LUSE volume is referred to as “a LUSE operation that handles a path-defined LDEV.”
When creating a LUSE volume in this manner, the following rules apply:
• You can combine an LDEV or LUSE volume having no path definitions with another LDEV or LUSE
volume having no path definitions.
• You can perform a LUSE operation that handles a path-defined LDEV regardless of how many paths
are defined to the LDEV.
• If you want to use an LDEV or a LUSE volume having no path definitions as the top LDEV of the
resulting LUSE volume, you cannot combine this LDEV or LUSE volume with other LDEVs or LUSE
volumes having path definitions.
When performing a LUSE operation that handles a path-defined LDEV:
• If a path is defined from a Windows 2000 host, a Windows Server 2003 host, or an AIX 5.2 host to
an LDEV, the LDEV can be used for LUSE operations that handle a path-defined LDEV. However, if a
path is defined from a host running another operating system to an LDEV, the LDEV cannot be used for
LUSE operations that handle a path-defined LDEV.
• If a path is defined from a Windows 2000 host or a Windows Server 2003 host to an LDEV and you
want to perform a LUSE operation that handles this path-defined LDEV, verify that the host mode of the
Windows host is 2C (Windows Extension). If the host mode is not 2C, change the host mode to 2C
before performing the LUSE operation.
• If the host mode is 0C (Windows Extension) and an LU path is defined for a volume, you cannot
perform LUSE operations on the volume without unmapping the volume first.
Custom Volume Size (CVS)
The Custom Volume Size (CVS) process configures custom volumes (CVs) that are smaller than normal
volumes. Custom volumes improve data access performance by reducing logical device contention as
well as host I/O queue times, which can occur when several frequently-accessed files are located on the
same volume.
If several frequently-accessed files are on the same LDEV, using CVS to set up smaller, separate custom
volumes for them can reduce conflicts and improve performance.
A small custom volume can be used as a command device. This leaves the rest of the LDEV free for other
uses.
CVS operations
CVS operations include the following: