Replication sets, Chapter 4 replication sets -1 – HP Storage Mirroring Software User Manual

Page 34

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Replication Sets

A replication set defines the data on a source machine that Storage

Mirroring protects. Replication sets are defined by volumes,

directories, files, or wild card combinations. Creating multiple

replication sets allows you to customize sets of data that need to be

protected.
When a replication set is created, a series of rules are defined that identify the volumes, directories,

files, and/or wild card combinations that will be replicated to the target. Each rule includes:

Path—The path including volume, drive, directory, file, and/or wild card

Include—If the specified path is to be included in the files sent to the target

Exclude—If the specified path is not to be included in the files sent to the target

Recursive—If the rule should automatically be applied to the subdirectories of the specified path

For example, a replication set rule might be

volume\directory\* inc, rec

This specifies that all files contained in the volume\directory path are included in the replication set.

Because recursion is set, all files and subdirectories under volume\directory are also included. A

complete replication set becomes a list of replication set rules.
Replication sets offer flexibility tailoring Storage Mirroring to your environment. For example, multiple

replication sets can be created and saved for a source to define a unique network configuration. There

may be three replication sets - Critical Data, User Data, and Offsite Data. Critical Data could be

configured to replicate, in real-time, to an onsite high-availability server. Offsite Data is replicated

across a WAN and, therefore, is configured to queue changes until a sufficient amount of data is

changed to justify transmission. At that point, the connection is made and stays active until all the

data is transmitted. User Data is not replicated throughout the day, but a nightly changed file mirror

copies only blocks of data that are different between the source and target server prior to a nightly

tape backup operation being run on the target server. Each of these replication sets can be automated

to transmit as needed, thus protecting your entire environment.
Keep in mind the following notes when creating and working with replication sets and connections.

Limitations

Replication set rules are limited in length meaning that the entire volume\directory\filename

including slashes, spaces, periods, extensions, cannot exceed 259 characters.

Storage Mirroring can mirror, replicate, verify, and restore paths up to 4,095 characters. Paths

longer than 4,095 characters will be skipped and logged to the Storage Mirroring log file and

the Linux system log.

Do not name replication sets or select a target location using illegal characters. Illegal

characters include the following.

Error checking and avoidance

Do not connect more than one replication set to the same location on a target. You could

overwrite or corrupt your data.

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.

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