Understanding Resynchronization; Synchronous Ip Mirrors; Asynchronous Ip Mirrors - HP Open View Installation And Maintenance Manual

Understanding resynchronization

This section describes the differences between resynchronizing synchronous and
asynchronous IP mirrors. It describes the following topics:

Synchronous IP mirrors

If the network goes down, synchronous IP mirroring (and all other network activity) stops.
During this down time, the appliance software tracks replication requests in the source LUN's
journal file. After you restore the network connection, the appliance software uses the journal
file to determine which data must be replicated on the target LUN.
Each resynchronization request requires a resynchronization thread. Any other requests
initiated before the network went down are waiting for and/or using available worker threads.
Therefore, the resynchronization and worker threads compete for network resources,
increasing traffic on the network and causing it to slow down.

Asynchronous IP mirrors

Resynchronization and heavy network use do not affect asynchronous IP mirrors.
Asynchronous IP mirroring only stops when:
The worker threads for asynchronous IP mirrors do not use the network; they only transfer
replication requests from the source LUN to the AIPM queue, which is a local connection.
Therefore, worker threads and resynchronization threads do not compete for network
resources.
Continuous Access Storage Appliance Installation and Maintenance Guide
Synchronous IP mirrors
Asynchronous IP mirrors
Common resynchronization issues
The asynchronous IP mirroring (AIPM) queue is full or drained.
You pause the asynchronous IP mirror.
IP Mirroring
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