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The "FAQ" page has been changed by DavidAllsopp: http://wiki.apache.org/cassandra/FAQ?action=diff&rev1=131&rev2=132 == What are seeds? == + Seeds are used during startup to discover the cluster + - If you configure your nodes to refer some node as seed, nodes in your ring tend to send Gossip message to seeds more often ( Refer to [[ArchitectureGossip]] for details ) than to non-seeds. In other words, seeds are worked as hubs of Gossip network. + If you configure your nodes to refer some node as seed, nodes in your ring tend to send Gossip message to seeds more often ( Refer to [[ArchitectureGossip]] for details ) than to non-seeds. In other words, seeds are worked as hubs of Gossip network. With seeds, each node can detect status changes of other nodes quickly. - With seeds, each node can detect status changes of other nodes quickly. + Seeds are also referred by new nodes on bootstrap to learn other nodes in ring. 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. - Seeds are also referred by new nodes on bootstrap to learn other nodes in ring. - 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. - If you configure a node as seed, it doesn't auto_bootstrap. So if you want to add a node to ring and make it seed, auto_bootstrap first, and then make it seed next. + Newer versions of cassandra persist the cluster topology making seeds less important then they were in the 0.6.X series, where they were used every startup + You can make a seed a node at any time. There is nothing special about seed nodes. If you list the node in seed list it is a seed + + Seeds do not auto bootstrap (ie if a node has itself in its seed list it will not automatically transfer data to itself) If you want a node to do that bootstrap it first and then add it to seeds later. If you have no data (new install) you do not have to worry about bootstrap or autobootstrap at all. + + Recommended usage of seeds: + * pick two (or more) nodes per data center as seed nodes. + * sync the seed list to all your nodes <<Anchor(seed_spof)>>
