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From Harsh J <ha...@cloudera.com>
Subject Re: Which server store the root and .meta. information?
Date Fri, 10 Feb 2012 15:46:07 GMT
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 <yongyong313@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 <harsh@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 <yongyong313@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 <rogerdai@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"<yongyong313@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

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