Question about HBase and region Servers

[#1]

1. What's the purpose of Region Server
2. Where is should be located ? Every datanode ?
3. What's the purpose of HBase Master
4. HBase is NoSql database. What does it store ?

[#2]

Great questions

1.region server stores hbase key regions, ranges of rows, that's where client would go to look up rows.

2. best practice is to colocate each RS with DD for better performance and advantage of short circuit reads

3. Master handles all metadata, DDL operations and region assignments.

4. HBase stores key/value pairs not unlike hashmap data structure. If you do a key lookup you get a value stored by that key.

[#3]

@Prakash Punj

What's the purpose of Region Server? Read this

Where is should be located ? Every datanode ?

You run RegionServers on the same servers as DataNodes. 

What's the purpose of HBase Master?

 HBase provides low-latency random reads and writes on top of HDFS and it’s able to handle petabytes of data. One of the interesting capabilities in HBase is Auto-Sharding, which simply means that tables are dynamically distributed by the system when they become too large.
The HBase Architecture has two main services: HMaster that is responsible for coordinating Regions in the cluster and execute administrative operations; HRegionServer responsible to handle a subset of the table’s data. 

HBase is NoSql database. What does it store ?

HBase is a distributed, nonrelational (columnar) database that utilizes HDFS as its persistence store for data.

Hope that answers you ..

[#4]

Best document to read more about these topics: Apache HBase ™ Reference Guide

[#5 · Accepted solution]

@Prakash Punj

What's the purpose of Region Server

In HBase the slaves are called Region Servers. Each Region Server is responsible to serve a set of regions, and one Region (i.e. range of rows) can be served only by one Region Server.

Where is should be located ? Every datanode ?

Yes

What's the purpose of HBase Master

HBase Master coordinates the HBase Cluster and is responsible for administrative operations.

HBase is NoSql database. What does it store ?

HDFS

See this http://www.slideshare.net/xefyr/h-base-for-architectspptx

[#6]

Thank you everyone...all great answers..