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Chapter 4 StorEdge File Replicator 4-7
FIGURE 4-4 The Mirror Log and Primary Journal
The Primary Journal floats through the Mirror Log functioning in a similar manner
to that in which it does now. Sun StorEdge 5310 NAS maintains hints in the
filesystem that enable it to quickly locate its position in both the Primary Journal and
Mirror Log if an outage (e.g., a complete power loss, component failure, etc.) is
experienced. As with all Sun StorEdge 5310 NAS products, the integrity of the
filesystem is guaranteed by the presence and use of the journal, irrespective of the
type of outage experienced.
4.1.4 Mirroring Variations
As with many technologies, there are a number of different ways mirroring can be
employed. These variations can be employed irrespective of the type of mirroring
(Checkpoint/Snapshot, Real-time/Synchronous or Pseudo Real-
time/Asynchronous) used.
4.1.4.1 Many-to-One Mirroring
In Many-to-One mirroring, several Master systems are mirrored to a single Mirror
target. Many-to-One mirroring is frequently used by customers for DR purposes, to
collect exact duplicates of multiple systems at multiple remote locations at a single,
central site, where recovery scenarios can be centrally managed. For instance, remote
departmental systems in Los Angeles, Houston and San Francisco might be mirrored
to a single corporate Datacenter in Kansas City. In the event any one of the remote