Partitions; Volumes - HP ML110 G1 User Manual

NOTE:
for additional information on LUN extension and use by the operating
system.

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 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
See the section "Dynamic Growth" in the administration guide
Storage Server user guide 29