Hardware And Software Components - HP StorageWorks P9000 User Manual

Remote replication occurs using journal volumes on the local and remote systems.
The journal on the local system is the "master journal".
The journal on the remote system is the "restore journal".
Replication occurs in the following sequence:
Journal obtain - When the host sends an update to the primary volume, the system's
journal-obtain function triggers a copy of the update data to the master journal volume.
◦ The host assigns write-sequence numbers to the data sent to the journal.
◦ Write-sequence numbers and other metadata attached to journal data insure consistency
with the data in the primary volume.
Journal copy - data is copied from the master journal to the restore journal.
◦ If the master journal has data, the primary system transfers it to the restore journal. When
data transfer is complete, master journal data is discarded.
Data copy to the restore journal is initiated by the read-journal command issued by the
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remote system.
Data copy occurs on a continual basis unless there is no data in the local journal. On
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storage system, journal reading operations are performed just after finished the former
read operation.
Journal-restore - the secondary volume is updated with changed data from the restore journal.
Data is copied to the secondary volume according to the write sequence numbers, insuring
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data consistency.
When journal-restore is completed, the data in the restore journal is discarded.
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NOTE:
In the configuration of Continuous Access Journal, the updating of data volumes and the
creating of journal data are processed. The performance of data volumes replicated with
Continuous Access Journal will be slightly lower than that of unreplicated data volumes.
The primary storage system does not remove the target journal data from its master journal
volume until it receives the sequence numbers of the restored journal that is given to the read
journal command from the secondary storage system. This is true even if the primary storage
system and secondary storage system are connected using a channel extender product.

Hardware and software components

A typical configuration consists of a P9500 or externally attached system on both local and remote
sites, a host or hosts connected to the systems, Continuous Access Journal software on both systems,
data path connections, and interface tools for configuring and managing Continuous Access
Journal.
The local and remote P9500 systems are connected using dedicated fibre channel data paths,
which can include fibre channel switches. Data paths are routed from the fibre channel ports
on primary system to the ports on the secondary system.
The host is connected to the P9500 using a fibre channel target port.
Remote Web Console is connected via a management LAN.
Hardware and software components 9