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From aaron morton <>
Subject Re: Cassandra backup queston regarding commitlogs
Date Mon, 30 Apr 2012 04:17:31 GMT
Each mutation is applied to the commit log before being applied to the memtable. On server
start the SSTables are read before replaying the commit logs. This is part of the crash only
software design and happens for every start.

AFAIk there is no facility to snapshot commit log files as they are closed. The best advice
would be to to keep them on a mirror set for durability. 


Aaron Morton
Freelance Developer

On 29/04/2012, at 1:04 AM, Roshan wrote:

> Hi
> Currently I am taking daily snapshot on my keyspace in production and
> already enable the incremental backups as well.
> According to the documentation, the incremental backup option will create an
> hard-link to the backup folder when new sstable is flushed. Snapshot will
> copy all the data/index/etc. files to a new folder.
> *Question:*
> What will happen (with enabling the incremental backup) when crash (due to
> any reason) the Cassandra before flushing the data as a SSTable (inserted
> data still in commitlog). In this case how can I backup/restore data?
> Do I need to backup the commitlogs as well and and replay during the server
> start to restore the data in commitlog files?
> Thanks.
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