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From Robert Coli <>
Subject Re: questions related to the SSTable file
Date Wed, 18 Sep 2013 01:01:45 GMT
On Tue, Sep 17, 2013 at 5:46 PM, Takenori Sato <> wrote:

> > So in fact, incremental backup of Cassandra is just hard link all the
> new SSTable files being generated during the incremental backup period. It
> could contain any data, not just the data being update/insert/delete in
> this period, correct?
> Correct.
> But over time, some old enough SSTable files are usually shared across
> multiple snapshots.

To be clear, "incremental backup" feature backs up the data being modified
in that period, because it writes only those files to the incremental
backup dir as hard links, between full snapshots.
When incremental backups are enabled (disabled by default), Cassandra
hard-links each flushed SSTable to a backups directory under the keyspace
data directory. This allows you to store backups offsite without
transferring entire snapshots. Also, incremental backups combine with
snapshots to provide a dependable, up-to-date backup mechanism.

What Takenori is referring to is that a full snapshot is in some ways an
"incremental backup" because it shares hard linked SSTables with other


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