HP Storage Mirroring Software - Manual (Page 100)

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! ! ! ! Replication
Replication
A file change, also called a file request or operation, is the creation, modification, or deletion of a file. This also includes file
attribute and permission changes. Replication is the real-time transmission of these file changes as they occur. The file changes
are replicated from the source to the target, maintaining an identical copy of data on the target machine.
Replication is the key to Storage Mirroring; without having identical copies of data on the source and target machines at all
times, the target would not be able to meet the high availability and disaster recovery needs of your complex network
environment.
Replication Options
Replication can be started automatically on connection, which is the default and recommended configuration, and it can also
be started and stopped manually at any time. Stopping replication is separate from stopping the transmission of data to the
target. When replication stops, data is not added to the queue on the source.
You can also turn off replication when you are not concerned about real-time backup, but want to use Storage Mirroring’s
block checksum mirror to periodically synchronize files.
How Replication Works
To better understand how Storage Mirroring replication works, the following diagram identifies the steps that occur when
data is replicated from the source to the target machine.
1. The file system handles all file requests when an application creates, modifies, or deletes data on the source machine.
2. The file requests are filtered by the Storage Mirroring File System Driver.
3. The Storage Mirroring File System Driver allows all file requests to be forwarded to the file system and to Storage
Mirroring.
4. The file system writes the operation to disk on the source machine.
5. Storage Mirroring converts the file requests into replication packets.
6. The Storage Mirroring source sends the replication packets to the Storage Mirroring target where they are applied to
the target copy of the data.
WARNING: When stopping replication, source/target data integrity is no longer guaranteed. A remirror will be necessary
to guarantee that the source and target data are identical.
Source Target
Application
- File System Driver
Operating System
Service
Disk
- File System