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From Lisen Mu <imm...@gmail.com>
Subject Re: Cassandra use cases: as a datagrid ? as a distributed cache ?
Date Thu, 29 Apr 2010 03:54:54 GMT
http://www.reddit.com/r/programming/comments/bcqhi/reddits_now_running_on_cassandra/

It seems to me that they are still using Cassandra in persistant storage
layer as a replacement of memcachedb, not in cache layer.

I'm new here with Cassandra actually, but now I'm also curious about the
possibility of using cassandra as cache.
the main concern is repair-on-read strategy, the secondary is commitlog.

If I'm correct about this, every read request to cassandra will trigger
several (N-1) message between cassandra nodes.
In our current traditional memcached + mysql set up, our intranet is kind of
busy already. I think It would be a burden if message is flooding between
memcached servers.

In fact, In my opinion, what happend to our db is happening again in cache
layer:

First, we have nonsql Cassandra, saver of the day.
But we are not going to let Cassandra carry the weight of page view
directly, so we still need cache.
Eventually we have to shard the cache to scale, and replicate to handle hot
spot.
In this stage, it would be a HUGE pity if we cannot reuse Cassandra's
exclusively outstanding ability of handling distribution problem.

So why not provide a kind of Cassandra Daemon, so we can write adapter for
memcached etc. to construct a pure-in-memory distributed cache layer?

On Tue, Apr 27, 2010 at 9:47 AM, Jonathan Ellis <jbellis@gmail.com> wrote:

> On Mon, Apr 26, 2010 at 9:04 AM, Dominique De Vito
> <dominique.devito@thalesgroup.com> wrote:
> > (1) has anyone already used Cassandra as an in-memory data grid ?
> > If no, does anyone know how far such a database is from, let's say,
> Oracle
> > Coherence ?
> > Does Cassandra provide, for example, a (synchronized) cache on the client
> > side ?
>
> If you mean an in-process cache on the client side, no.
>
> > (2) has anyone already used Cassandra as a distributed cache ?
> > Are there some testimonials somewhere about this use case ?
>
> That's basically what reddit is using it for.
> http://blog.reddit.com/2010/03/she-who-entangles-men.html
>
> --
> Jonathan Ellis
> Project Chair, Apache Cassandra
> co-founder of Riptano, the source for professional Cassandra support
> http://riptano.com
>

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