HP StorageWorks 2000 Modular Smart Array Reference Guide (481599-003, August 2008)

176 HP StorageWorks 2000 Family Modular Smart Array reference guide • August 2008
Disk Space Usage Statistics
As an Advanced user, you can view information about overall disk space usage for
all disk drives in the storage system.
The following information is displayed about virtual disk space, excluding spares.
Field Description
Volume Space Space for user data storage.
Free Space Space allocated for a virtual disk but not used by volumes.
Free space in a virtual disk can be used to add an additional
volume to that virtual disk or to expand a volume in that
virtual disk. There are three ways free space can be created:
• When a virtual disk is created, space that is reserved for
volume expansion is free space.
• If a virtual disk is expanded by adding a disk then the
new capacity becomes free space.
• If a volume is deleted then the freed capacity will revert
to free space.
RAID Protection Space Space used for mirroring or Error Correction Code (ECC)
data. This is the data that enables the virtual disk to
continue to function even if a disk is lost.
Backoff Space Space reserved to compensate for minor capacity
differences between disk drives so that they can be used
interchangeably. The backoff value can be changed by
service technicians for testing but cannot be changed
through the end-user interfaces.
Not Usable Because of
Different Drive Sizes
This category is displayed if a virtual disk contains
different size drives. Because the usable amount of space
on any disk drive in a RAID virtual disk is equal to the size
of the smallest disk drive, space on larger disk drives is
unusable. For example, if a virtual disk contains 500-Gbyte
disks and a 250-Gbyte disk, half of the space on each larger
disk is unusable.