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https://issues.apache.org/jira/browse/CASSANDRA-12805?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15609197#comment-15609197
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Jon Haddad commented on CASSANDRA-12805:
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A couple notes on some improvements I think should be made.
{quote}+In the event that Cassandra crashes, any updates that haven't been
commited to the `SSTables` would be lost. Commitlogs
+provides durability for a Cassandra node by syncronizing the `Memtables` to
disk. When starting the Cassandra node, it
+will load the SSTables then apply any updates in the commitlog to the
memtables. {quote}
Commitlogs are an append only log of all mutations local to a Cassandra node.
Any data written to Cassandra will first be written to a commit log before
being written to a memtable. This provides durability in the case of
unexpected shutdown. On startup, any mutations in the commit log will be
applied.
For the different commit log sync options, It would be more informative to list
them in clearly defined sections (and use the help text from the yaml) like
follows:
The commit log has the following options which control how it is synced to disk:
* batch: When in batch mode, Cassandra won't ack writes until the commit log
has been fsynced to disk. It will wait commitlog_sync_batch_window_in_ms
milliseconds between fsyncs. This window should be kept short because the
writer threads will be unable to do extra work while waiting. You may need to
increase# concurrent_writes for the same reason.
* periodic: In periodic mode, writes are immediately ack'ed, and the CommitLog
is simply synced every commitlog_sync_period_in_ms milliseconds.
> Website documentation for commitlog
> -----------------------------------
>
> Key: CASSANDRA-12805
> URL: https://issues.apache.org/jira/browse/CASSANDRA-12805
> Project: Cassandra
> Issue Type: Improvement
> Components: Documentation and Website
> Reporter: Hau Phan
> Priority: Minor
> Labels: documentation
> Attachments: 12805-trunk.txt
>
>
> Updated Storage Engine page for commitlogs
> Commit:
> https://github.com/nothau/cassandra/commit/876d395b4188bb230f869a161c3d7fe317506b34
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