Using Cci With Thin Image - Hitachi VSP F1500 User And Reference Manual

ShadowImage and TrueCopy operations continue unattended to provide
continuous data backup.
There are specific requirements for using ShadowImage and TrueCopy in
high-availability (HA) configurations. UNIX/PC servers in HA configurations
normally support disk duplication functions to enhance disk reliability (for
example, mirroring provided by the LVM or device driver, RAID5 or an
equivalent function provided by the LVM). UNIX/PC servers also feature hot
standby and mutual hot standby functions in case of failures on the server
side. However, mutual hot standby for disaster recovery has not yet been
achieved since it requires the remote mirroring function.
ShadowImage provides the mirroring function within the storage system. For
detailed information about ShadowImage operations, please see the Hitachi
ShadowImage® User Guide for your storage system.
TrueCopy provides remote mirroring functionality, linkage functionality with
failover switching, and remote backup operations among servers, all of which
are required by UNIX/PC servers in HA configurations for disaster recovery.
For detailed information about TrueCopy operations, please see the Hitachi
TrueCopy® User Guide for your storage system.

Using CCI with Thin Image

CCI allows you to perform Hitachi Thin Image operations by issuing raidcom
commands (for example, raidcom add snapshot) to the RAID storage
system. Hitachi Thin Image stores snapshots in storage system. Creating a
Thin Image pair changes the status to "PAIR" and stores snapshot data as a
copy of the data on the Thin Image P-VOL. A Thin Image pair consists of a P-
VOL, one or more S-VOLs that are virtual volumes (V-VOLs), and one or more
pool-VOLs that are LDEVs. P-VOL differential data is stored as snapshot data
in the pool-VOLs. If your storage system experiences a data storage failure,
you can restore the data using the snapshot data in the pool. Splitting a Thin
Image pair saves a snapshot and stops the copying of replaced data in the
pool.
Consistency groups and snapshot groups are groups of pairs for which you
can simultaneously perform pair tasks on all pairs within the group. You can
use CCI raidcom commands to create consistency groups and snapshot
groups and to split pairs to store the snapshot data for the groups.
• A consistency group can include HTI, SI, and SIz pairs. Splitting the pairs
using the group assures data consistency at the time the storage system
receives the request.
• A snapshot group is a group of only Thin Image pairs. Use consistency or
snapshot groups to perform Thin Image tasks on all of the pairs within
the group. You define Thin Image pairs to a snapshot group when you
create the pairs.
Note: When you use the CCI to define multiple Thin Image pairs in a
consistency group, you can only specify one consistency group for a group
defined in the CCI configuration definition file.
6-4
Data replication operations with CCI
Command Control Interface User and Reference Guide