HP LUN Configuration Manager XP Software - Manual (Page 60)

60 HP StorageWorks LUN Configuration Manager XP: user’s guide
Note the following limitations:
• You cannot combine LDEVs from different control units.
• Windows NT hosts cannot access more than 32 logical units.
• Some operating systems may experience slow disk access times with
large logical units.
The following are guidelines for LU Size Expansion:
• A maximum of 256 expanded LUNs can be configured on the same
port.
• The LDEVs that will become members of the LUSE must not have
SCSI paths assigned. These are known as free (or available) LDEVs.
• To make an LDEV free, it must have its SCSI paths deleted, which
requires that it be offline (unmounted from all hosts).
• Combining nonsequential LDEVs into a LUSE is supported, provided
they are on the same CU.
• Combining customized volumes into a LUSE is supported, provided
they have the same size, emulation type, and CU. The order of
operations is important: you must first create the volumes, and then
combine those volumes into a LUSE volume.
• Combining customized volumes and normal volumes into the same
LUSE is not supported.
• Combining command devices into a LUSE is not supported.
• Combining RAID1 and RAID5 into the same LUSE is not supported.
• Combining emulation types (OPEN-x) into the same LUSE is not
supported.
• Factors relevant to recommended LUSE size include the following:
Some operating systems may exhibit slow disk access times with large
logical units if they contain too many high usage files. The size of a
LUSE can also affect the amount of time required to perform backups.
• The queue depth for open systems can vary depending on the platform.