HP Storage Mirroring V5.1 Software - Manual (Page 40)

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Replication sets contain error checking to avoid inadvertent overwrites of the replication set
rules. When replication sets are modified, a generation number is associated with the
modifications. The generation number is incremented anytime the modifications are saved,
but the save is not allowed if there is a mismatch between the generation number on the
source and the Management Console. You will be notified that the replication set could not be
saved. This error checking safeguards the replication set data in the event that more than one
client machine is accessing the source’s replication sets.

Storage Mirroring will not replicate the same data from two different replication sets on your
source. The data will only be replicated from one of the replication sets. If you need to
replicate the same data more than once, connect the same replication set to multiple targets.

If you rename the root folder of a connected replication set, Storage Mirroring interprets this
operation as a move from inside the replication set to outside the replication set. Therefore,
since all of the files under that directory have been moved outside the replication set and are
no longer a part of the replication set, those files will be deleted from the target copy of the
replication set. This, in essence, will delete all of your replicated data from the target. If you
have to rename the root directory of your replication set, make sure that the replication set
is not connected.

When creating replication sets, keep in mind that when recursive rules have the same type
(include or exclude) and have the same root path, the top level recursive rule will take
precedence over lower level non-recursive rules. For example, if you have c:\data included
recursively and c:\data\logs included nonrecursively, the top level rule, c:\data, will take
precedence and the rule c:\data\logs will be discarded. If the rules are different types (for
example, c:\data is included and c:\data\logs is excluded), both rules will be applied as
specified.
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Including and excluding files

Do not exclude Microsoft Office temporary files from your replication set. When a user opens
a Microsoft Office file, a temporary copy of the file is opened. When the user closes the file,
the temporary file is renamed to the original file and the original file is deleted. Storage
Mirroring needs to replicate both the rename and the delete. If you have excluded the
temporary files from your replication set, the rename operation will not be replicated, but the
delete operation will be replicated. Therefore, you will have missing files on your target.

When Microsoft SQL Server databases are being replicated, you should always include the
tempdb files, unless you can determine that they are not being used by any application. Some
applications, such as PeopleSoft and BizTalk ® , write data to the tempdb file. You can, most
likely, exclude temporary databases for other database applications, but you should consult
the product documentation or other support resources before doing so.

Some applications create temporary files that are used to store information that may not be
necessary to replicate. If user profiles and home directories are stored on a server and
replicated, this could result in a significant amount of unnecessary data replication on large
file servers. Additionally, the \Local Settings\Temporary Internet Files directory can easily
reach a few thousand files and dozens of megabytes. When this is multiplied by a hundred
users it can quickly add up to several gigabytes of data that do not need to be replicated.

Creating replication sets that only contain one file may cause unexpected results. If you need
to replicate just one file, add a second file to the replication set to ensure the data is replicated
to the correct location. (The second file can be a zero byte file if desired.)

Backups

Storage Mirroring does not replicate the last access time if it is the only thing that has
changed. Therefore, if you are performing incremental or differential backups on your target
machine, you need to make sure that your backup software is using an appropriate flag to
identify what files have been updated since the last backup. You may want to use the last
modified date on the file rather than the date of the last backup.

Virus protection

Virus protection software on the target should not scan replicated data. If the data is protected
on the source, operations that clean, delete, or quarantine infected files will be replicated to
the target by Storage Mirroring. If the replicated data on the target must be scanned for
viruses, configure the virus protection software on both the source and target to delete or
quarantine infected files to a different directory that is not in the replication set. If the virus
software denies access to the file because it is infected, Storage Mirroring will continually
attempt to commit operations to that file until it is successful, and will not commit any other
data until it can write to that file.