HP 3PAR Operating System Software - Manual (Page 47)

Fully provisioned virtual volumes and Thin volumes have three separate data components:
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User space contains the user data . The user space is the area of the volume that corresponds
to the regions in the CPG that are available to the host. Thus, the user space is the part of the
virtual volume you export to the host as a LUN.
•
Copy space, also known as snapshot space, contains the copy data. The copy space is the
area of the volume that corresponds to the regions in the CPG that contain copies of user data
that have changed since the previous virtual copy (snapshot) of the volume was created.
•
Administration space, also known as admin space, contains pointers to copies of user data
in the copy space. The administration space is the area of the volume that corresponds to
regions in the CPG that track changes to the volume that occurred after the previous snapshot
was created. Administration space is managed by the system; it cannot be exported and
cannot be removed from the system.
You can provision a virtual volume’s user space and copy space from the same or from different
CPGs. If a virtual volume’s user space and copy space are on different CPGs and if the CPG
containing the copy space becomes full, the user space still remains available to the host.
To save time, you can create multiple identical virtual volumes at one time.
Physical Copies
A physical copy is a full copy of a volume. A physical copy duplicates all the data from one original
base volume to another volume called the destination volume. The data in a physical copy is static;
it is not updated with subsequent changes to the parent volume. Therefore, any changes to either
volume causes them to lose synchronization with each other; however, you can resynchronize the
volumes. For more information about how to resynchronize a base and destination volume, see
the HP 3PAR Management Console Online Help.
To reduce the number of management tasks that involve physical copies, you can:
•
Create a consistent group of physical copies from a list of virtual volumes.
•
Group physical copies into autonomic groups that are managed as one physical copy.
A physical copy can be made only from a base volume that has enough free space to accommodate
writes to that volume during the physical copy operation. In addition, the destination volume must
meet the following conditions:
•
It must have snapshot space associated with it.
•
It must have at least as much user space as the volume being copied.
•
It must not be exported to a host.
Virtual Copies
A virtual copy is a snapshot of a base volume, which is an original volume that is copied. Unlike
a physical copy, which is a duplicate of an entire volume, a virtual copy records only changes to
the base volume. This functionality allows an earlier state of the original virtual volume to be
re-created by starting with its current state and rolling back all the changes that were made after
the virtual copy was created.
To create virtual copies, the HP 3PAR Virtual Copy license is required.
You can make virtual copies of the following items:
•
Fully provisioned virtual volumes
•
Thin volumes
•
Physical copies
•
Other virtual copies (snapshots)
Physical Copies 47