incubator-cassandra-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Edward Capriolo <>
Subject Re: How expensive are additional keyspaces?
Date Tue, 11 Mar 2014 15:17:06 GMT
I am not sure. As stated the only benefit of multiple keyspaces is if you

1) different replication per keyspace
2) different multiple data center configurations per keyspace

Unless you have one of these cases you do not need to do this. I would
always tackle this problem at the application level using something like:

Client issues aside, it is not a very common case and I would advice
against uncommon set ups.

On Tue, Mar 11, 2014 at 11:08 AM, Keith Wright <> wrote:

> Does this whole true for the native protocol?  I've noticed that you can
> create a session object in the datastax driver without specifying a
> keyspace and so long as you include the keyspace in all queries instead of
> just table name, it works fine.  In that case, I assume there's only one
> connection pool for all keyspaces.
> From: Edward Capriolo <>
> Reply-To: "" <>
> Date: Tuesday, March 11, 2014 at 11:05 AM
> To: "" <>
> Subject: Re: How expensive are additional keyspaces?
> The biggest expense of them is that you need to be authenticated to a
> keyspace to perform and operation. Thus connection pools are bound to
> keyspaces. Switching a keyspace is an RPC operation. In the thrift client,
> If you have 100 keyspaces you need 100 connection pools that starts to be a
> pain very quickly.
> I suggest keeping everything in one keyspace unless you really need
> different replication factors and or network replication settings per
> keyspace.
> On Tue, Mar 11, 2014 at 10:17 AM, Martin Meyer <>wrote:
>> Hey all -
>> My company is working on introducing a configuration service system to
>> provide cofig data to several of our applications, to be backed by
>> Cassandra. We're already using Cassandra for other services, and at
>> the moment our pending design just puts all the new tables (9 of them,
>> I believe) in one of our pre-existing keyspaces.
>> I've got a few questions about keyspaces that I'm hoping for input on.
>> Some Google hunting didn't turn up obvious answers, at least not for
>> recent versions of Cassandra.
>> 1) What trade offs are being made by using a new keyspace versus
>> re-purposing an existing one (that is in active use by another
>> application)? Organization is the obvious answer, I'm looking for any
>> technical reasons.
>> 2) Is there any per-keyspace overhead incurred by the cluster?
>> 3) Does it impact on-disk layout at all for tables to be in a
>> different keyspace from others? Is any sort of file fragmentation
>> potentially introduced just by doing this in a new keyspace as opposed
>> to an exiting one?
>> 4) Does it add any metadata overhead to the system keyspace?
>> 5) Why might we *not* want to make a separate keyspace for this?
>> 6) Does anyone have experience with creating additional keyspaces to
>> the point that Cassandra can no longer handle it? Note that we're
>> *not* planning to do this, I'm just curious.
>> Cheers,
>> Martin

View raw message