This document provides guidelines for planning the layout of services in a MapR HA cluster. It recommends: - Running the TaskTracker and MapR-FS on most worker nodes - Running control services like the CLDB, ZooKeeper, JobTracker on a few nodes - Avoiding running ZooKeeper and CLDB on the same node, especially for clusters over 100 nodes - Maintaining additional machines for failover purposes It includes an example service layout and a table with recommended instances of services like CLDB, HBase, JobTracker, ZooKeeper, and others to use when designing a HA cluster service layout.

1. LAB: Configuration July 2012
LAB: Planning
Goal
In these exercises you will designa MapR HACluster by planningthe service layout.
This is a theoretical exercise and at the end you will review other student’s MapR
HA Cluster design.
Exercise: Planning: Review Service Layout in a small cluster
Planning involveswhich services to run on which nodes in the cluster.
 The majority of nodes are worker nodes, which run the TaskTracker
and MapR-FS services for data processing.
 A few nodes run control services that manage the cluster and
coordinate MapReduce jobs.
Here is an example of the control service layout on a small cluster:
Most clusters run the CLDB on three nodes and ZooKeeper on three or five
nodes. For details and sample configurations, see Planning the Deployment.
The following guidelines will help you refine the service layout.
 ZooKeeper and CLDB
If possible, avoid running ZooKeeper and CLDB on the same node
(especially in clusters over 100 nodes).
 TaskTracker on CLDB or ZooKeeper nodes
If you must run TaskTracker on CLDB or ZooKeeper nodes, reduce the
number of task slots by half (see Tuning MapReduce).
© 2012 by MapR Technologies Page 1 of 3

2. LAB: Configuration July 2012
 JobTracker on CLDB
Avoid running the JobTracker on the master CLDB node. You can
configure the JobTracker and CLDB on the same nodes as long as the
running JobTracker and the master CLDB do not reside on the same
node; if failover causes the JobTracker and CLDB to run on the same
node, rectify the problem as quickly as practical.
 JobTracker on ZooKeeper nodes
Avoid running the JobTracker on nodes that are running ZooKeeper.
 Set up a pool of machines for failover
Maintain additional machines for failover; these machines can be
normal nodes running the TaskTracker until they are needed.
Exercise: Planning: Design Service Layout for HA Cluster
You are going to design your own HA Cluster and review with other students.
The instructor will give you a planning sheet to record your cluster design.
Draw the racks and name them Rack1, Rack2, … RackN, and label the
Services per the following example:
Layout the services using the following table asa guideline for the number of
instances of each service to run in thecluster:
© 2012 by MapR Technologies Page 2 of 3

3. LAB: Configuration July 2012
Service Package How Many
CLDB (CLDB) mapr-cldb 1-3
FileServer (FS) mapr-fileserver Most or all nodes
HBase Master (HM) mapr-hbase-master 1-3
HBaseRegionServer mapr-hbase- Varies
(HR) regionserver
JobTracker (JT) mapr-jobtracker 1-3
NFS mapr-nfs Varies
TaskTracker (TT) mapr-tasktracker Most or all nodes
WebServer (WS) mapr-webserver One or more
Zookeeper (ZK) mapr-zookeeper 1, 3, 5, or a higher odd
number
© 2012 by MapR Technologies Page 3 of 3