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From Apache Wiki <wikidi...@apache.org>
Subject [Hadoop Wiki] Trivial Update of "ZooKeeper/ProjectDescription" by jeremyhanna
Date Thu, 09 Dec 2010 23:35:59 GMT
Dear Wiki user,

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The "ZooKeeper/ProjectDescription" page has been changed by jeremyhanna.
The comment on this change is: Fixed typo..
http://wiki.apache.org/hadoop/ZooKeeper/ProjectDescription?action=diff&rev1=4&rev2=5

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

  
  Read requests sent by a !ZooKeeper client are processed locally at the !ZooKeeper server
to which the client is connected. If the read request registers a watch on a znode, that watch
is also tracked locally at the !ZooKeeper server. Write requests are forwarded to other !ZooKeeper
servers and go through consensus before a response is generated. Sync requests are also forwarded
to another server, but does not actually go through consensus. Thus, the throughput of read
requests scales with the number of servers and the throughput of write requests decreases
with the number of servers.
  
- Order is very important to !ZooKeeper. (They tend to be a bit obsessive compulsive.) All
updates are totally order. !ZooKeeper actually stamps each update with a number that reflects
this order. We call this number the zxid (!ZooKeeper Transaction Id). Each update will have
a unique zxid. Reads (and watches) are ordered with respect to updates. Read responses will
be stamped with the last zxid processed by the server that services the read.
+ Order is very important to !ZooKeeper. (They tend to be a bit obsessive compulsive.) All
updates are totally ordered. !ZooKeeper actually stamps each update with a number that reflects
this order. We call this number the zxid (!ZooKeeper Transaction Id). Each update will have
a unique zxid. Reads (and watches) are ordered with respect to updates. Read responses will
be stamped with the last zxid processed by the server that services the read.
  

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