On Tue, Sep 17, 2013 at 5:46 PM, Takenori Sato <ts...@cloudian.com> 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. http://www.datastax.com/docs/1.0/operations/backup_restore " 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 snapshots. =Rob
