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DOCS-871 multithreaded replication #666

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Feb 21, 2013
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DOCS-871 multithreaded replication #666

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16 changes: 16 additions & 0 deletions source/core/replication-internals.txt
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Expand Up @@ -304,6 +304,22 @@ behaviors:
value, either ``true`` or ``false``, for the
:data:`members[n].buildIndexes` field.

Multithreaded Replication
-------------------------

MongoDB supports multithreaded replication by applying write operations
on secondary nodes in batches. Each batch is divided among many threads.
The multithreaded writes allow for concurrent CPU usage.

Despite the multithreaded writes, reads on secondaries do not "see"
operations applied out of order. While the threads are writing, MongoDB
blocks read operations, even if the write operations yield.

Before writing a batch of oplog operations, MongoDB fetches all the
memory pages that contain the data and indexes to be written. The
prefetch stage minimizes the amount of time MongoDB must hold the write
lock to apply operations.

Pre-Fetching Indexes to Improve Replication Throughput
------------------------------------------------------

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