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From Narendra Sharma <narendra.sha...@gmail.com>
Subject Re: seed faq
Date Thu, 21 Apr 2011 06:57:58 GMT
Here are some more details that might help:
1. You are right that Seeds are referred on startup to learn about the ring.
2. It is a good idea to have more than 1 seed. Seed is not SPoF. Remember
Gossip also provides eventual consistency. So if seed is missing, the new
node may not have the correct view of the ring. However, after talking to
other nodes it will eventually have the uptodate state of the ring.
3. In an iteration Gossiper on a node sends gossip message
 - To a known live node (picked randomly)
 - To a known dead node (based on some probability)
 - To a seed node (based on some probability)

Thanks,
Naren

On Wed, Apr 20, 2011 at 7:13 PM, Maki Watanabe <watanabe.maki@gmail.com>wrote:

> I made self answered faqs on seed after reading the wiki and code.
> If I misunderstand something, please point out to me.
>
> == What are seeds? ==
>
> Seeds, or seed nodes are the nodes which new nodes refer to on
> bootstrap to know ring information.
> When you add a new node to ring, you need to specify at least one live
> seed to contact. Once a node join the ring, it learns about the other
> nodes, so it doesn't need seed on subsequent boot.
>
> There is no special configuration for seed node itself. In stable and
> static ring, you can point non-seed node as seed on bootstrap though
> it is not recommended.
> Nodes in the ring tend to send Gossip message to seeds more often by
> design, so it is probable that seeds have most recent and updated
> information of the ring. ( Refer to [[ArchitectureGossip]] for more
> details )
>
> == Does single seed mean single point of failure? ==
>
> If you are using replicated CF on the ring, only one seed in the ring
> doesn't mean single point of failure. The ring can operate or boot
> without the seed. But it is recommended to have multiple seeds in
> production system to maintain the ring.
>
>
>
> Thanks
> --
> maki
>



-- 
Narendra Sharma
Solution Architect
*http://www.persistentsys.com*
*http://narendrasharma.blogspot.com/*

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