3.6.1 HP PolyServe Matrix Server Administration Guide (T5392-96018, August 2008)

Chapter 7: Configure the SAN 66
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 matrix
contain unsupported partitions. The Alert will remain until the disks
with unsupported partitions are deported.
Maximum Length for Disk UIDs
The maximum length for a Matrix Server disk UID is 128 characters. If a
disk UID exceeds this limit, Matrix Server will not be able to import the
disk into the matrix. 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 Matrix Server. The
Windows operating system renumbers partitions when a lower-
numbered partition is deleted. Matrix Server uses the partition number
when it is identifying membership partitions and dynamic volumes.
Changes to the partition numbers will causes failures, as Matrix Server
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
I/O operations. The exact alignment characteristics vary by manufacturer
and model; consult your storage vendor for alignment recommendations.