HP NAS 4000s, Administration Manual

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Storage Management Overview
62 NAS 4000s and 9000s Administration Guide
or be mounted as mount points on existing disks. If mount points are utilized, it should be
noted that Services for UNIX 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 are limited to no more than 32 separate
LUNs with each LUN not exceeding 2 terabytes (TB). Volumes also cannot exceed 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 be a bad 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. It should be noted that if a
dynamic disk goes offline, then 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, once 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. Please note that 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. In general, HP
recommends utilizing the Array controller for the management of fault tolerance over the use
of Windows Storage Server 2003 software RAID since it places an additional level of
operating system overhead on volumes. If mount points are utilized, it should be noted that
Services for UNIX does not support mount points at this time.
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.
Note: Dynamic disks cannot be used for clustering configurations because Microsoft Cluster only
supports basic disks.
Utilizing Storage Elements
No matter which type of storage element is created in the WebUI the last step in creating the
element is determining its drive letter or mount point and formatting the element. Each
element created can exist as a drive letter(s), assuming one is available and/or as mount points
off of an existing folder of a drive letter. Either method is supported. However, mount points