HP P6000 SmartStart Storage Software - Manual (Page 31)

existing virtual disks. It does not include space on physical disks that are not members of a
disk group.
•
Allocated capacity. The storage space that is currently used by existing virtual disks on an HP
P6000 storage system, or P6000 storage network.
This does not include unallocated space in disk groups, nor space on physical disks that are
not members of a disk group.
•
Available capacity. The storage space in disk groups that currently is not being used by existing
virtual disks on an HP P6000 storage system, or P6000 storage network. This space can be
used to create new virtual disks or increase the size of existing virtual disks.
See also Disk group capacity , Physical disk drive capacity and Virtual disk capacity .
Thin provisioning
Thin provisioning is a licensed feature of HP P6000 storage systems (with controller software XCS
10000000) which allows you to create and manage thin provisioned virtual disks.
NOTE: To create thin provisioned virtual disks, you must use HP P6000 Command View. See
Running HP P6000 Command View .
The key features of thin provisioned virtual disks differ from standard virtual disks in several
significant ways:
•
The amount of physical disk space which is allocated to a thin provisioned virtual disk can
automatically change in response to the amount of data being stored, up to the specified size
of the virtual disk. A traditional virtual disk requires the full amount of physical disk space to
be allocated at all times.
•
A well planned thin provisioned virtual disk does not require explicit resizing (manually or
with scripts). With a traditional virtual disk, any time the size needs to be changed, it must
be explicitly resized.
•
There is no unused physical disk space associated with a thin provisioned virtual disk, thus
physical disk space cannot become stranded. With a traditional virtual disk, the allocated but
unused physical disk space can create stranded capacity.
•
The requested capacity for a thin provisioned virtual disk can actually exceed the amount of
physical disk drive capacity that can be allocated. This is not possible with traditional virtual
disks.
Example
This example demonstrates each of the points above.
A storage administrator is planning to create two virtual disks for two new host applications. The
HP P6000 storage system currently has at total capacity of 10 TB, with 6 TB free.
The administrator determines that each host application initially needs 2 TB of disk space, but in
the future, as the amount of data increases, the host applications will need 4 TB of space. With
these requirements in mind, the administrator creates two 4 TB thin provisioned virtual disks.
Each host application sees its virtual disk as having a capacity of 4 TB, even though only 2 TB of
physical disk space is initially allocated. As the amount of stored data increases, the storage system
automatically allocates more space (up to the 4 TB maximum size).
And, even though only 6 TB of space is free on the storage system, the administrator is able to
add 2 virtual disks with a total potential capacity of 8 TB.
Allocation alarms and email notification are used by the administrator to monitor data increases
and send email notifications.
Licensing
Thin provisioning 31