HP StorageWorks X3000 Network Storage Systems - Manual (Page 51)

It is important to note that a LUN may span all physical drives within a storage controller subsystem,
but cannot span multiple storage controller subsystems.
Figure 18 Two arrays (A1, A2) and five logical drives (L1 through L5) spread over five physical drives
.
NOTE:
This type of configuration may not apply to all storage systems and serves only as an example.
Through the use of basic disks, you can create primary partitions or extended partitions. Partitions
can only encompass one LUN. Through the use of dynamic disks, you can create volumes that span
multiple LUNs. You can use the Windows Disk Management utility to convert disks to dynamic and
back to basic and to manage the volumes residing on dynamic disks. Other options include the ability
to delete, extend, mirror, and repair these elements.
Partitions
Partitions exist as either primary partitions or extended partitions. The master boot record (MBR) disk
partitioning style supports volumes up to 2 terabytes in size and up to 4 primary partitions per disk
(or three primary partitions, one extended partition, and unlimited logical drives). Extended partitions
allow the user to create multiple logical drives. These partitions or logical disks can be assigned drive
letters or be used as mount points on existing disks. If mount points are used, it should be noted that
Services for UNIX (SFU) does not support mount points at this time. The use of mount points in
conjunction with NFS shares is not supported.
The GUID partition table (GPT) disk partitioning style supports volumes up to 18 exabytes in size and
up to 128 partitions per disk. Unlike MBR partitioned disks, data critical to platform operation is
located in partitions instead of unpartitioned or hidden sectors. In addition, GPT partitioned disks
have redundant primary and backup partition tables for improved partition data structure integrity.
On the Volumes tab in the disk properties dialog box in Disk Management, disks with the GPT
partitioning style are displayed as GUID Partition Table (GPT) disks, and disks with the MBR partitioning
style are displayed as Master Boot Record (MBR) disks.
Volumes
When planning dynamic disks and volumes, there is a limit to the amount of growth a single volume
can undergo. Volumes are limited in size and can have no more than 32 separate LUNs, with each
LUN not exceeding 2 terabytes (TB), and volumes totaling no more than 64 TB of disk space.
The RAID level of the LUNs included in a volume must be considered. All of the units that make up a
volume should have the same high-availability characteristics. In other words, the units should all be
of the same RAID level. For example, it would not be a good practice to include both a RAID 1+0
and a RAID 5 array in the same volume set. By keeping all the units the same, the entire volume retains
the same performance and high-availability characteristics, making managing and maintaining the
volume much easier. If a dynamic disk goes offline, the entire volume dependent on the one or more
X1000 and X3000 Network Storage System 51