Zero downtime backup and HP StorageWorks Continuous Access EVA

Data Protector A.05.10 - ZDB for EVA in the CA Configuration
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3.4.3 Data Replication Group States
Each DR group in CA EVA can be in one of the following states: "normal", "error", "warning", "unknown". Only when a DR group is
in the "normal" or "warning" state, the data on the destination virtual disks is always consistent with the data on the destination virtual
disks (of the same copy sets). Other states do not guarantee this consistency.
The "suspend" mode of a DR group indicates that data replication of the belonging source virtual disks is suspended. Changes to the
existing data located on these virtual disks are logged to the CA EVA log until data replication is resumed. In the "suspend" mode, the
state of the DR group is set to "logging".
3.5 Snapshot Backup on the CA EVA
During snapshot backup on an EVA+BC, a replica of the virtual disks is created on the EVA disk array first and then backed up to the
tape media.
On CA EVA, the ZDB for CA EVA extension enables two variants of ZDB to be performed with Data Protector:
• The destination virtual disks of the copy sets (DR groups) are backed up (the replica is created on the remote disk array).
• The source virtual disks of the copy sets (DR groups) are backed up (the replica is created on the local disk array).
In either case, the backup system must have access to the virtual disks being backed up. The tape device can be located on an arbitrary
place, as long as it is visible from the backup system.
By default, running the first ZDB variant, that is, backup of the destination virtual disks, succeeds only if the involved DR groups are in
the "normal" or "warning" state, as in these cases the consistency of the backed up data is guaranteed. However, there are situations,
when you are willing to sacrifice data consistency in favour of performing a ZDB session for the destination virtual disks. For such
occasions, you can specify additional ZDB options that enable ZDB sessions even when the involved DR groups are in the "error" or
"warning" state. Note that in the latter cases, the consistency of the backed up data is not guaranteed.
3.6 Layout of a Data Protector Cell Using the CA EVA Configuration
In a Data Protector cell where ZDB sessions are performed using the CA EVA, three systems in the cell have special roles: Cell
Manager, application system, and backup system. Cell Manager has a standard role in the cell, and can host Windows Server 2003 or
any other operating system that supports the Data Protector ZDB functionality. Application system is a Data Protector client that uses
the source virtual disks of CA EVA for data storage. Backup system is a Data Protector client that must have access to the source virtual
disks (if backup of the source virtual disks will be performed) or the destination virtual disks (if backup of the destination virtual disks
will be performed).
The three roles can be physically implemented with one, two, or three hosts. However, having the application system and backup
system implemented with two different hosts has the following advantages:
• The performance of the applications running on the application system does not degrade during backup from the replica on the
remote disk array to tape media.
• If the EVA disk arrays are located on sites on different physical locations, and backup of the destination virtual disks is performed,
during the ZDB session the SAN between the sites will not increase, provided the network is configured properly.