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Planned downtime

Plan your downtime

An enterprise can use a number of existing technologies and processes to control its planned downtime. by Radha Shelat

Many companies have implemented clustering, volume management, and replication technologies as a line of defence against unplanned downtime. These may be caused by server failures, site outages, and other events and can affect customer service levels.

However technology can also be leveraged to reduce costs and outages associated with planned downtime events and help provide a significant Return on Investment (RoI).

Escalating planned downtime

Planned downtime refers to any planned administrative operation that can potentially interrupt or slow down service in areas such as a server upgrade, data movement, server consolidation, or site maintenance.

Planned downtime occurs more often than unplanned partly because hardware systems have grown more robust and resilient over time, and the average duration between failures is constantly improving.

The frequency of scheduled downtime processes in most enterprises is rising. A data centre in a large enterprise may run multiple classes of applications, on hundreds or even thousands of systems. Administrators may schedule modifications almost daily in order to reconfigure systems, and perform upgrades or apply patches. Depending upon the processes that are in place, any modification may result in downtime.

Major concern

Performing routine operations, namely upgrades and patches, without disrupting service is a major concern for companies today. The immediacy of online services has produced a culture of end users who do not tolerate delay.

In online businesses, for example, an outage or slowdown that lasts five minutes is almost guaranteed to drive impatient customers to competitors' sites for goods and services. If customers experience the delay again, they may never come back. From the revenue and site branding standpoints, these are serious concerns.

Leveraging Disaster Recovery solutions

Data protection and Disaster Recovery solutions can be leveraged for planned downtime operations, dramatically shrinking both administrative costs and outage windows. These tools automate procedures to make administrators more efficient, reduce the possibility of human error, and accelerate processes that may have an impact on end users.

Typical scenarios

The term 'planned downtime' is in fact an oxymoron. The downtime associated with most planned operations that could potentially affect uptime can be eliminated.

For instance, automated real-time replication of volumes can move data transparently in a vendor-independent manner to other servers at any location worldwide. Automated stateful failover can move a live application to another server without interrupting services. A clustering solution can migrate an entire data centre to another location.

Let''s look at some typical examples.

Scenario one: Migrating an application

You want to move all your users to another server. There is no server available within the data centre, so you have to move the application, with all its user groups and data, to a server in a data centre that is two time zones away.

Volume management and replication software can mirror the data to a storage centre at a distant location. Clustering software can move the application to a new server in a failover operation that preserves the state of the application and its user data. These planned, automated operations can carry out the migration with virtually no impact on service levels and allow users to continue accessing their data and application without incurring the downtime normally associated with application migration.

Scenario two: Upgrading Microsoft Exchange

You are running Exchange in a non-clustered, non-automated environment, and you need to upgrade it with a new service pack. You are forced to shut down the server and cut-off user access to what is arguably their most critical application.

You then have to load the new service pack and the new application, point the application to the data, and redirect your clients to the new server. If on the other hand, you're running Exchange in a clustered environment, performing upgrades has a minimal impact on users.

With automated clustering and volume management tools, copying the data to a disk and migrating the Exchange application service to another server within the cluster is a push-button operation that can save hours of downtime.

Scenario three: Server consolidation

You have a number of stand-alone systems in your environment that are not generating the RoI that they could. A decision is made to bring in a new class of server and storage hardware that can be configured with multiple domains.

Using clustering technology that you may have acquired as part of your solution, you simply add each stand-alone system to the new cluster and execute a migration command to move the application over. Your consolidation ratio is 12:1 (in this hypothetical case), and you wind up with a much smaller footprint for those applications translating to higher reliability and availability. You can perform the same amount of work with fewer servers and reduce your hardware and maintenance costs.

Scenario four: Performance-based migration

You have applications running in an environment where performance levels are not satisfactory. The time required to process a transaction and to respond to a mouse click on a Web page has reached a point where your monitoring software is sending alerts.

Your disaster recovery solution includes a cluster server and a cluster file system that helps you migrate the applications, permanently or temporarily, to systems that are better able to handle the service. The process is automated and there is no need to do a restart on the new node. You eliminate downtime while maintaining application performance.

The bottom line

The bottom line is speed, efficiency, and cost reduction. Clustering, replication and volume management tools that comprise an effective high availability or disaster recovery solution can contribute handsomely to your RoI when they act as facilitators of planned downtime projects. One obvious benefit is that they are already in place at most companies making additional expenditure unnecessary.

Another powerful benefit is that these tools automate procedures, reduce administrative costs, increase efficiency and eliminate the possibility of error. Many highly automated routine procedures can be initiated remotely by administrators or run at predetermined intervals.

Significant benefit

The most significant benefit, however, is the ability of these tools to reduce downtime to a matter of seconds. Using stateful migration, users can be migrated to another set of systems without the need for them to reconnect, thereby significantly reducing the downtime associated with planned maintenance. The connection is persistent, and the state of the application is maintained, even for users who were conducting transactions.

Unforeseen events and site outages will happen. However, clustering, replication and volume management technologies can be leveraged to ensure the availability of data and applications, minimise the impact of failures on a business and ultimately align IT with business operations while significantly increasing an enterprise's RoI.

Radha Shelat is the Chief Technology Officer of Veritas Software India.

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