HP StorageWorks Storage Mirroring Scripting Guide (T2558-96327, April 2009)

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17 - 5

Creating a backup of the target by rotating

connections

The following two scripts create multiple copies of your data on the target, but only one copy is active

at a time. This allows you the time and availability to backup the inactive copy of data. This is

especially helpful when you have applications with interdependent files.

Backups occur sequentially from the first file to the last file. Therefore, when you are using

applications that have interdependent files, such as a database application whose database and log

files must be synchronized, Storage Mirroring cannot be actively updating files on the target while

the backup is running, or there becomes an opportunity for interdependent files to become

mismatched, causing a corrupt application on the backup. For example, suppose the following

scenario occurs on a target machine that contains a replica of a database.

1. The backup process which is currently running sequentially through the files on the target,

reaches the database log file and starts writing the log file to tape. At the same time, Storage

Mirroring receives additional updates to the database. The database file on the target is updated,

but since the log file is in use by the backup, the associated log operation is placed on the

Storage Mirroring queue on the target.

2. When the log file is finished being backed up, the backup process continues with the next

sequential file, which is not necessarily the database that corresponds with that log file.

3. Since the log file is no longer in use, Storage Mirroring applies the log operation from the

Storage Mirroring queue.

4. Eventually, the backup process reaches the database file and writes it to tape.

At this point, the database file on the tape backup contains an extra update that the log file on the

tape backup does not. The two files do not correspond, so the database on the tape backup will not

be time consistent.

The two scripts identify an existing connection, disconnect it, establish a new connection, and initiate

a difference mirror. The connections in the two scripts transmit the same data to two different

locations, allowing you to backup the idle files on the inactive connection.

REM Script 1

$TheSource = "alpha";

$TheTarget = "beta";

$TheUser = "admin";

$ThePassword = "password";

$TheDomain = "domain.com";

$TheRepSet = "DataFiles";

source $TheSource;

$FirstConnection = conid $TheRepSet to $TheTarget map base c:\first_location;

disconnect $FirstConnection;

$SecondConnection = connect $TheRepSet to $TheTarget map base c:\second_location, nomirror;

mirror start $SecondConnection different, checksum;

REM Script 2

$TheSource = "alpha";

$TheTarget = "beta";

$TheUser = "admin";

$ThePassword = "password";

$TheDomain = "domain.com";

$TheRepSet = "DataFiles";

source $TheSource;

$SecondConnection = conid $TheRepSet to $TheTarget map base c:\second_location;

disconnect $SecondConnection;

$FirstConnection = connect $TheRepSet to $TheTarget map base c:\first_location, nomirror;

mirror start $FirstConnection different, checksum;