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From Aaron Morton <>
Subject Re: Seed Nodes
Date Wed, 02 Mar 2011 22:16:27 GMT
The seed list is also used as part of the Gossip round 

I agree it's not critical to ensure all running nodes have the same running seed list. But
it's definitely a good idea. 

Disclaimer: Learning more about the gossip protocol is on my to-do list :)


On 03 Mar, 2011,at 08:27 AM, Nick Bailey <> wrote:

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.

Some info on seeds here

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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