You do not need to restart when changing the seedlist of nodes that are up. The seedlist is really only used when a node first starts. So if you modify the list of seeds the changes will take effect whenever that node restarts, exactly when they need to.

In 0.7 you can basically get away with ignoring the seedlist for nodes that have already joined the cluster since the ring state is remembered between restarts. "Best Practices" may dictate that you keep all your seed lists updated though.

On Tue, Mar 1, 2011 at 9:29 PM, Eric Gilmore <> wrote:
Yes, two per DC is a recommendation I've heard from Jonathan Ellis.  We put that in yet more documentation at (appreciate the citation Aaron :)

I had a recent conversation with a Cassandra expert who had me convinced that, as long as a node online already had one seed in its list at startup, you wouldn't really need to restart it -- at least right away -- after adding a second seed to the config.  Rather than confuse the issue by trying to remember/recreate the rationale for that, I'll ping him and see if he'll comment here.

On Tue, Mar 1, 2011 at 12:04 PM, Aaron Morton <> wrote:
AFAIK it's recommended to have two seed nodes per dc.

You will need a restart.


On 2/03/2011, at 6:08 AM, wrote:

How many seed nodes should I have for a cluster of 100 nodes each with about 500gb of data? Also to add seeds the nodes, must I change the seed nodes list on all existing nodes through the Cassandra.yaml file? Will changes take effect without restarting the node?


Shan (Susie) Lu,  Analyst

Accenture Technology Labs - Silicon Valley

cell  +1 425.749.2546   



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