The client does communicate with the master to perform .META. changing interactions (create/delete tables, etc.). And for the rest, like locating regions off regionservers and reading off them, the master isn't touched (afaik).
The master's work is also more about running/providing cluster management services for the many region servers than serving clients all the while. See the interfaces HMasterRegionInterface and MasterServices on trunk to get a view of what all functions the master carries out, on a high level, and why its role is important though clients may not need it beyond administrative purposes. 2012/2/10 yonghu <yongyong...@gmail.com>: > Thanks for your reply. If the -ROOT- and .META. tables are managed by > two RegionServer separately. What is the functionality of Master node? > It only assigns the Region node in the cluster? So, the client only > needs to contact with these two special RegionServer which contains > the -ROOT- and .META. tables. If the interaction model is like what I > said, the client will not contact with master node! If I am wrong, > let me know. > > Thanks > > Yong > > On Fri, Feb 10, 2012 at 12:47 PM, Harsh J <ha...@cloudera.com> wrote: >> The HMaster does not host regions, and the -ROOT- is a region; It is >> hosted by one of the assigned RegionServers, and its location is >> registered under ZooKeeper. The -ROOT- region then holds the location >> of the .META. (Which again, is another region, and is hosted by >> RegionServers in just the same way). >> >> For your ZK question, if you run ZK in HBase's embedded mode, it runs >> on the HMaster, while if you run it standalone you can choose to run >> it anywhere. The latter method is what is recommended for production >> deployments, and its preferable to host it separately on its own >> boxes. >> >> P.s. The JIRA at https://issues.apache.org/jira/browse/HBASE-3171 may >> simplify this someday :) >> >> 2012/2/10 yonghu <yongyong...@gmail.com>: >>> Thanks! >>> I know this. I just want to know which nodes store this information >>> when the client first contact to HBase cluster, HMaster or >>> RegionServer or a special node in which runs the zookeeper. >>> >>> And the other question is whether zookeeper runs on the same nodes as >>> Hbase in the cluster or it runs in a separate nodes? >>> >>> Yong >>> >>> On Fri, Feb 10, 2012 at 12:16 PM, Roger <roger...@qq.com> wrote: >>>> To my knowledge, it is a three level tree-like structure. >>>> ------------------ >>>> 该邮件从移动设备发送 >>>> >>>> ------------------ Original ------------------ >>>> From: "yonghu"<yongyong...@gmail.com> >>>> Date: Fri, Feb 10, 2012 07:12 PM >>>> To: "user"<user@hbase.apache.org>; >>>> Subject: Which server store the root and .meta. information? >>>> >>>> >>>> Hello, >>>> >>>> I read some articles which mention before the client connect to the >>>> master node, he will first connect to the zookeeper node and find the >>>> location of the root node. So, my question is that the node which >>>> stores the root information is different from master node or they are >>>> the same node? >>>> >>>> Thanks! >>>> >>>> Yong >> >> >> >> -- >> Harsh J >> Customer Ops. Engineer >> Cloudera | http://tiny.cloudera.com/about -- Harsh J Customer Ops. Engineer Cloudera | http://tiny.cloudera.com/about
