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Figure 6 Two arrays (A1, A2) and

ve logical drives (L1 through L5) spread over

ve physical drives

NOTE:

This type of con

guration may not apply to all storage servers and serves only as an example.

Through the use of basic disks, primary partitions or extended partitions can be created. Partitions

can only encompass one LUN. Through the use of dynamic disks, volumes can be created that span

multiple LUNs. The Windows Disk Management utility can be used to convert disks to dynamic and back

to basic, and 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 and can be composed of only one basic

disk no larger than 2 TB. Basic disks can also only contain up to four primary partitions, or three primary

partitions and one extended partition. In addition, the partitions on them cannot be extended beyond the

limits of a single LUN. 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.

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 of

ine, 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

y 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 either. Therefore, selection of the volume

type is important. The same performance characteristics on numbers of reads and writes apply when

using fault-tolerant con

gurations, 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 ef

cient. 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.

HP ProLiant Storage Server