HP StorageWorks XP Remote Web Console Software - Manual (Page 11)

1 Overview of copy solutions
HP StorageWorks XP12000/XP10000/SVS200 arrays provide an extensive suite of data replication
software. This chapter describes HP StorageWorks Snapshot XP. This chapter also covers portions of
HP StorageWorks Business Copy XP because Snapshot XP is an integrated feature of Business Copy XP.
NOTE:
The use of Snapshot XP, Business Copy XP, 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.
Snapshot XP
Snapshot XP, like Business Copy XP, enables you to create multiple real-time online local copies of
logical volumes. Snapshot XP enables applications and solutions such as zero-downtime backup and
disaster recovery. While Business Copy XP creates complete copies, Snapshot XP creates space-efficient
copies that replicate only data from the primary volume that was rewritten. It uses less disk space, thus
reducing costs. Snapshot XP is supported on open systems such as UNIX and PC servers. Snapshot
XP is an integrated feature of Business Copy XP.
Snapshot XP creates pairs of primary volumes (P-VOLs) and secondary volumes (S-VOLs). Snapshot XP
secondary volumes are partial copies containing only changed P-VOLs. Snapshot XP is also known as
Copy-on-Write Snapshot. Snapshot XP 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 Snapshot XP creates is called a Snapshot XP pair.
Figure 1 illustrates the mechanism Snapshot XP uses to copy data in the array.
HP StorageWorks Snapshot XP user guide 11