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 dynamic disks is unavailable. There could be a potential for data loss depending
on the nature of the failed LUN.
Volumes are created out of the dynamic disks, and can be expanded on the fly to extend over
multiple dynamic disks if they are spanned volumes. However, after a type of volume is selected,
it cannot be altered. For example, a spanning volume cannot be altered to a mirrored volume
without deleting and recreating the volume, unless it is a simple volume. Simple volumes can be
mirrored or converted to spanned volumes. Fault-tolerant disks cannot be extended. Therefore,
selection of the volume type is important. The same performance characteristics on numbers of
reads and writes apply when using fault-tolerant configurations, as is the case with controller-based
RAID. These volumes can also be assigned drive letters or be mounted as mount points off existing
drive letters.
The administrator should carefully consider how the volumes will be carved up and what groups
or applications will be using them. For example, putting several storage-intensive applications or
groups into the same dynamic disk set would not be efficient. These applications or groups would
be better served by being divided up into separate dynamic disks, which could then grow as their
space requirements increased, within the allowable growth limits.
File system elements
File system elements are composed of the folders and subfolders that are created under each logical
storage element (partitions, logical disks, and volumes). Folders are used to further subdivide the
available file system, providing another level of granularity for management of the information
Storage management elements
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