You can use JMX over ssh by doing this:
http://blog.reactive.org/2011/02/connecting-to-cassandra-jmx-via-ssh.html
Basically, you use SSH -D to do dynamic application port forwarding.

In terms of scaling, you'll be able to afford 120GB RAM/node in 3 years if you're successful. Or, a machine with much less RAM and flash-based storage. :)
Seriously, though, the formula in the tuning guidelines is a guideline. You can probably get acceptable performance with much less. If not, you can shard your app such that you host a few Cfs per cluster. I doubt you'll need to though.


From: openvictor Open <openvictor@gmail.com>
Reply-To: <user@cassandra.apache.org>
Date: Mon, 4 Apr 2011 18:24:25 -0400
To: <user@cassandra.apache.org>
Subject: Re: Abnormal memory consumption

Okay, I see. But isn't there a big issue for scaling here ?
Imagine that I am the developper of a certain very successful website : At year 1 I need 20 CF. I might need to have 8Gb of RAM. Year 2 I need 50 CF because I added functionalities to my wonderful webiste will I need 20 Gb of RAM ? And if at year three I had 300 Column families, will I need 120 Gb of ram / node ? Or did I miss something about memory consuption ?

Thank you very much,

Victor

2011/4/4 Peter Schuller <peter.schuller@infidyne.com>
> And about the production 7Gb or RAM is sufficient ? Or 11 Gb is the minimum
> ?
> Thank you for your inputs for the JVM I'll try to tune that

Production mem reqs are mostly dependent on memtable thresholds:

  http://www.datastax.com/docs/0.7/operations/tuning

If you enable key caching or row caching, you will have to adjust
accordingly as well.

--
/ Peter Schuller