5.2.4 Constant backup by copying and mirroring a disk
You can use the disk copy and mirroring functionality# provided by hardware to constantly back up the contents of a disk.
- #
-
The TrueCopy function of Hitachi disk array systems is an example.
Copy the disk you want to back up as the main volume to the disk used for backup (remote volume). Because the contents of the main volume are constantly backed up, you can switch the connection to the remote volume and continue operation if the main volume can no longer be used due to a hardware failure or similar problem.
- Organization of this subsection
(1) Prerequisite conditions
The following are the prerequisite conditions for constant backup of a disk.
-
The hardware for the disk to be backed up must have the following specifications:
-
The order in which data is written to the main and remote volumes is guaranteed.
-
It must be guaranteed that the hardware ensure consistency between the main and remote volumes if data copying between shared disks stops.
-
Write protection of the remote volume must be guaranteed during data copying between shared disks.
-
-
The version of JP1/AJS3 - Manager must be 09-10 or later.
-
The JP1/AJS3 database must be a standard configuration or a standard configuration without ISAM.
-
A logical host environment must be used.
-
If JP1/AJS3 operates in a cluster system, the conditions described in 10.1.1 Prerequisites for JP1/AJS3, and the scope supported by JP1/AJS3 in the JP1/Automatic Job Management System 3 Administration Guide must be satisfied.
(2) Support scope
The scope of JP1/AJS3 support is the same as when JP1/AJS3 is used for disaster recovery. See 11.1.2(2) Support scope in the JP1/Automatic Job Management System 3 Administration Guide.
(3) System configuration
The following figure shows an example of a system configuration that uses constant backup of a disk.
|
|
![[Figure]](GRAPHICS/ZH050000.GIF)
(4) Method of operation
Use the disk copy and mirroring functionality of the hardware to start and stop copying, and to check the status. These functions are not provided by JP1/AJS3.
Note that the disk copy and mirroring functionality of the hardware might degrade the performance of the general operation of jobs (job definition, execution, and display). Therefore, make sure that you test the operation of jobs while data is being copied before using the disk copy and mirroring functionality in live operation.
(5) Precautionary note
When switching the connection from the main volume to the remote volume, perform a disaster-recovery start of JP1/AJS3 to resume operation. For details about a disaster-recovery start, see 6.2.1 Temporarily changing the start mode of JP1/AJS3 in the JP1/Automatic Job Management System 3 Administration Guide.