Google Search Appliance Configuring GSA Mirroring version 7.2 - Manual (Page 6)

Google Search Appliance: Configuring GSA Mirroring 6
In scenario two, both search appliances are freshly installed and the content is being crawled for the
first time. The master search appliance produces checkpoint files with newly-crawled content. The
checkpoint files will be of a moderate size and will take somewhat more time to transfer than in scenario
one. However, when the content has been fully crawled, the two search appliances will be in the same
steady state as the search appliances in scenario one: the delta between them is small, checkpoint files
are small and the synchronization process is rapid.
In scenario three, the master search appliance has fully crawled a corpus of 10 million documents. The
replica search appliance is freshly installed. The full set of checkpoint files from the master search
appliance must by synchronized by the replica search appliance. A large amount of data is transferred
initially. Eventually, the two search appliances reach the steady state of the search appliances in
scenario one.
The GSA mirroring diagnostics page on the Admin Console provides information about the current
synchronization process.
Most administrative configuration takes place on the master search appliance. Some configuration
information and all index data are replicated automatically and continuously to the replicas.
For information about which configuration data is copied to replicas, see “Settings that are Copied or
Not Copied to the Replica Search Appliances.”
Only the master search appliance crawls the content, minimizing the load on content servers and the
network. The replica search appliances do not crawl the content, but they can serve the index created
on the master node.
Note that the composite collections feature found under Admin Console > Index > Composite
Collections applies only to search appliance unified environments. You cannot use composite
collections with GSA mirroring.
The most common GSA mirroring configuration has one master search appliance and one replica. In the
following diagram, three search appliances are configured for GSA mirroring. A search appliance
designated as a master search appliance has two replicas, Replica 1 and Replica 2.