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From Tatu Saloranta <>
Subject Re: How reliable is cassandra?
Date Tue, 30 Mar 2010 18:11:52 GMT
On Mon, Mar 29, 2010 at 10:31 AM, Matthew Stump <> wrote:
> Am I crazy to want to switch our server's primary data store from postgres to cassandra?
 This is a system used by banks and governments to store crypto keys which absolutely can
not be lost.

Back to original question: in my completely personal opinion, you
probably should only consider this if you have a very good reason to
have to do it.
Cassandra is a very promising system, but given all the development, I
would not risk my career by storing absolutely-never-to-be-lost data.
One benefit of existing RDBMSs is that they have good data
export/backup tools; DBAs that can take over responsibility of
managing these aspects and son.

One important follow-up questions is this: do you really only need one
system? Most succeful large-scale systems I have worked on use
two-part division:

(a) Management system on RDBMS (oracle etc) -- ACID modifications, backups
(b) Delivery system possibly using something else (extensive caching;
key/value store; read-only replicas)

and with one-way synchronization from (a) to (b), with some delay --
be that via message queue, snapshots, whatever. Main benefit: linear
scalability for (b); ACID guarantees for (a).
"one system to store it all" view tends to be overvalued nowadays,
over "right tool for the job".

And for (b) I would absolutely seriously consider Cassandra or other
nosql systems.
But at least for now, not use it for (a).

Just my 2c,

-+ Tatu +-

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