Database Reference
In-Depth Information
The service level availability that you determine will have a significant
impact on your high-availability design. Some organizations will determine
that they need 99.9% uptime, whereas others will be primarily using their
bigdatasolutionforreportingandanalysisandwillcometoanumbercloser
to 95% being appropriate for them. Although 4.9% doesn't sound like a big
difference, that is a total of almost 18 days per year in downtime.
There are two different types of downtime that you must be concerned with:
scheduled and unscheduled downtime. Scheduled downtime is the type of
downtime that occurs when you schedule maintenance on your system. For
example, you could be scheduling downtime for applying a patch of your
software that requires a reboot of the system. In addition, you may schedule
downtime for an upgrade of your system software.
In contrast, unscheduled downtime arises from unplanned events such as
hardware or software failures. This unscheduled downtime could occur for
many reasons from as mundane as a power outage to as significant as
security breach such as a virus or other malware. In addition, events that
cause downtime include network outages, hardware failures, and software
failures.
For scheduled maintenance, you will need to shut down the NameNode
service. Toensure thecontrolled shutdown oftheservice, followthesesteps:
1. Shut down the NameNode monitoring agent:
service stop hmonitor-namenode-monitor
2. Shut down the NameNode process:
service stop hadoop-namenode
When maintenance is complete, follow these steps:
1. Start the NameNode process:
service start hadoop-namenode
2. Start the NameNode monitoring agent:
service start hmonitor-namenode-monitor
3. Verify that the monitoring process has started:
