HP StorageWorks Clustered File System 3.6.0 Windows Storage Server Edition Administration Guide (403103-005, January 2008)

Chapter 7: Configure the SAN 64
may have created dynamic volumes using those higher-numbered
partitions.
The higher-numbered partitions will continue to work correctly;
however, you should be aware of the following:
• A new volume cannot include subdevices having partition numbers
above 31. Existing volumes cannot be extended to include the higher-
numbered partitions.
• You will not be able to take a hardware snapshot of partitions with
numbers above 31.
• A single Alert will be issued if any disks or volumes in the cluster
contain unsupported partitions. The Alert will remain until the disks
with unsupported partitions are deported.
Maximum Length for Disk UIDs
The maximum length for an HP Clustered File System disk UID is 128
characters. If a disk UID exceeds this limit, HP Clustered File System will
not be able to import the disk into the cluster. If you are using a disk array
such as iSCSI that allows you to specify a disk volume name as part of the
UID, be sure that the total UID does not contain more than 128 characters.
Restriction for Disk Partitions
Do not delete disk partitions on LUNs accessed by HP Clustered File
System. The Windows operating system renumbers partitions when a
lower-numbered partition is deleted. HP Clustered File System uses the
partition number when it is identifying membership partitions and
dynamic volumes. Changes to the partition numbers will causes failures,
as HP Clustered File System cannot locate the correct data.
Disk Partition Alignment
Many disk arrays are sensitive to misaligned I/O operations and require
I/O to be aligned on block boundaries for performance reasons. For
example, an array may “prefer” to have I/O operations occur on natural
block boundaries, such as 4-KB blocks. If a partition starts at a non-block
boundary, a single logical write can span more physical blocks that it
would on a partition starting on a block boundary, resulting in additional