HP StorageWorks XP Remote Web Console Software - Manual (Page 7)

1 Overview of copy solutions
HP StorageWorks XP12000/XP10000/SVS200 arrays provide an extensive suite of data replication
software. This chapter describes HP StorageWorks XP Snapshot. This chapter also covers portions of
HP StorageWorks XP Business Copy because XP Snapshot is an integrated feature of XP Business
Copy.
NOTE:
The use of XP Snapshot, XP Business Copy, and all other software products is governed by the terms
of your license agreements with Hewlett-Packard.
IMPORTANT:
This guide contains information about internal disks or LDEVs. Unlike the XP12000/XP10000 Disk
Arrays, the SVS200 has no internal disks. Therefore, information about internal disks or LDEVs does
not apply to the SVS200.
XP Snapshot
XP Snapshot, like XP Business Copy, enables you to create multiple real-time online local copies of
logical volumes. XP Snapshot enables applications and solutions such as zero-downtime backup and
disaster recovery. While XP Business Copy creates complete copies, XP Snapshot creates space-efficient
copies that replicate only data from the primary volume that was rewritten. It uses less disk space,
thus reducing costs. XP Snapshot is supported on open systems such as UNIX and PC servers. XP
Snapshot is an integrated feature of XP Business Copy.
XP Snapshot creates pairs of primary volumes (P-VOLs) and secondary volumes (S-VOLs). XP Snapshot
secondary volumes are partial copies containing only changed P-VOLs. XP Snapshot is also known
as Copy-on-Write Snapshot. XP Snapshot secondary volumes are partial copies containing only the
data that has been changed in the P-VOLs. Pointers kept in mapping tables allow access to secondary
volumes through virtual volumes (V-VOLs). The S-VOL is composed of data in the pool-VOL (old data
that has since changed in the P-VOL) and data in the P-VOL (data that has not changed yet). The
P-VOL/S-VOL pair that XP Snapshot creates is called a XP Snapshot pair.
Figure 1 on page 8 illustrates the mechanism XP Snapshot uses to copy data in the array.
XP Snapshot User Guide 7