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From Apache Wiki <wikidi...@apache.org>
Subject [Cassandra Wiki] Update of "FAQ_JP" by MakiWatanabe
Date Sat, 23 Apr 2011 15:01:38 GMT
Dear Wiki user,

You have subscribed to a wiki page or wiki category on "Cassandra Wiki" for change notification.

The "FAQ_JP" page has been changed by MakiWatanabe.
The comment on this change is: Add #seed and #seed_spof.
http://wiki.apache.org/cassandra/FAQ_JP?action=diff&rev1=82&rev2=83

--------------------------------------------------

   * [[#replicaplacement|Cassandraはどのデータがどのノードに配置されているかをどのように判定しますか?]]
   * [[#cachehitrateunits|JMXで行キャッシュあるいはキーキャッシュのヒット率が0.XX123456789のように表示されます。これはXX%という意味でしょうか?それとも0.XX%でしょうか?]]
   * [[#bigcommitlog|Commit Logが大変肥大化しています。Cassandraは古いCommit
Logを削除しないのでしょうか?]]
+  * [[#seed|What are seeds?]]
+  * [[#seed_spof|Does single seed mean single point of failure?]]
+ 
  
  
  <<Anchor(cant_listen_on_ip_any)>>
@@ -499, +502 @@

  
  update column family XXX with memtable_flush_after=60;
  
+ <<Anchor(seed)>>
+ 
+ 
+ == What are seeds? ==
+ 
+ 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.
+ 
+ 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.
+ 
+ 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.
+ 
+ 
+ <<Anchor(seed_spof)>>
+ 
+ == 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. However, it will need more time to spread status changes of node over
the ring.
+ It is recommended to have multiple seeds in production system.
+ 

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