HP NAS 4000s, Administration Manual

Page: 61 / 246

Storage Management Overview
61 NAS 4000s and 9000s Administration Guide
Online Spares
Further protection against data loss can be achieved by assigning an online spare (or hot spare)
to any configuration except RAID 0. This hard drive contains no data and is contained within
the same storage sub system as the other drives in the array. When a hard drive in the array
fails, the controller can then automatically rebuild information that was originally on the failed
drive onto the online spare. This quickly restores the system to full RAID level fault tolerance
protection. However, unless RAID ADG is being used, which can support two drive failures in
an array, in the unlikely event that a third drive in the array should fail while data is being
rewritten to the spare, the logical drive will still fail.
Physical Storage Best Practices
Minimally, choosing the best disk carving strategy includes the following policies:
■
Analyze current corporate and departmental structure.
■
Analyze the current file server structure and environment.
■
Plan properly to ensure the best configuration and use of storage.
— Determine the desired priority of fault tolerance, performance, and storage capacity.
— Use the determined priority of system characteristics to determine the optimal striping
policy and RAID level.
■
Include the appropriate number of physical drives in the arrays to create LUNs of desired
sizes.
Logical Storage Elements Overview
Logical Storage elements consist of those components that translate the physical storage
elements to the file system elements as presented in
Figure 23 . The NAS server utilizes the
WebUI to manage the various types of disk presented to the file system. The WebUI has two
types of LUN presentation, basic disk and dynamic disk. Each of these types of disk has
special features that enable different types of management. Through the use of basic disks,
primary partitions or extended partitions may be created. Partitions can only encompass one
LUN. Through the use of dynamic disks, volumes can be created that span multiple LUNS.
The WebUI 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.
The sections below briefly discuss each of these types of representations and the
considerations that need to be observed.
More detailed information regarding the WebUI for disk management activities can be
obtained in the Disk Management Chapter.
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