Introducing HBase - HBase Essentials - page 13

• RegionServers : In HBase, horizontal scalability is deined with a term called
region. Regions are nothing but a sorted range of rows stored continuously.
In HBase architecture, a set of regions is stored on the region server. By
default, the region server runs on port 60030. In an HBase cluster based
on HDFS, Hadoop DataNodes and RegionServers are typically called
slave nodes as they are both responsible for server data and are usually
collocated in the cluster. A list of the region servers is speciied in the conf /
regionservers ile with each region server on a separate line, and the start/
stop of these region servers is controlled by the script iles responsible for an
HBase cluster's start/stop.
• HBase data storage system : HBase is developed using pluggable architecture;
hence, for the data storage layer, HBase is not tied with HDFS. Rather, it can
also be plugged in with other ile storage systems such as the local ilesystem
(primarily used in standalone mode), S3 (Amazon's Simple Storage Service),
CloudStore (also known as Kosmos ilesystem) or a self-developed ilesystem.
Apart from the mentioned components, there are other considerations as well, such
as hardware and software considerations, that are not within the scope of this topic.
The backup HBase Master server and the additional region servers can
be started in the pseudo-distributed mode using the utility provided
bin directory as follows:
[root@localhost hbase-0.96.2-hadoop2]# bin/local-
master-backup.sh 2 3
The preceding command will start the two additional HBase Master
backup servers on the same box. Each HMaster server uses three ports
( 16010 , 16020 , and 16030 by default) and the new backup servers
will be using ports 16012 / 16022 / 16032 and 16013 / 16023 / 16033 .
[root@localhost hbase-0.96.2-hadoop2]# bin/local-
regionservers.sh start 2 3
The preceding command will start the two additional HBase region
servers on the same box using ports 16202 / 16302 .
Start playing
Now that we have everything installed and running, let's start playing with it and
try out a few commands to get a feel of HBase. HBase comes with a command-
line interface that works for both local and distributed modes. The HBase shell
is developed in JRuby and can run in both interactive (recommended for simple
commands) and batch modes (recommended for running shell script programs).
Let's start the HBase shell in the interactive mode as follows:
[root@localhost hbase-0.98.7-hadoop2]# bin/hbase shell