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From Jonathan Ellis <>
Subject Re: backing up data from cassandra
Date Mon, 05 Oct 2009 17:15:50 GMT
On Mon, Oct 5, 2009 at 11:23 AM, Thorsten von Eicken <> wrote:
> Isn't the question about how you back up a cassandra cluster, not a
> single node?

Sure, but the generalization is straightforward. :)

> Can you snapshot the various nodes at different times or do
> they need to be synchronized?

The closer the synchronization, the more consistent they will be.
(Since Cassandra is designed around eventual consistency, there's some
flexibility here.  Conversely, there's no way to tell the system
"don't accept any more writes until the snapshot is done.")

> Is there a minimal set of nodes that are
> sufficient to back up?

Assuming your replication is 100% up to date, backing up every N nodes
where N is the replication factor could be adequate in theory, but I
wouldn't recommend trying to be clever like that, since if you
"restored" from backup like that your system would be in a degraded
state and vulnerable to any of the restored nodes failing.


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