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From Eric Charles <e...@apache.org>
Subject Re: Which server store the root and .meta. information?
Date Sat, 11 Feb 2012 08:02:18 GMT
Hypothetical case (probably asked a number of time here, sorry...):

Can a client correcty put, get, scan (no admins tasks such as create
table,...) with a HBase cluster having its HMaster process down  ?

(if really the case, 'master' could be renamed to 'admin' to make it
clear that it is 'optional').

Thx,
Eric


On 10/02/12 20:00, Doug Meil wrote:
> 
> Also, there is a description of what is in META and ROOT in here...
> 
> http://hbase.apache.org/book.html#arch.catalog
> 
> ... and it also describes the startup sequencing.
> 
> 
> 
> 
> 
> On 2/10/12 10:46 AM, "Harsh J"<harsh@cloudera.com>  wrote:
> 
>> 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
>>
> 

-- 
eric | http://about.echarles.net | @echarles

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