SDA India is an online resource for Software, Development,IT, Architecture, Open Source, Mobile, Security, Databases, Delphi, C, OS, Asp, .Net, Php, Xml, Java

"Before we get down to debunking the four myths, let’s step back and take a high-level look at high availability. If high availability is your goal, what downtime threats do you need to protect against?" questions C M Woon in his article Debunking the Common Myths of High Availability. There are many, but they can be consolidated under six categories:

• Data Corruption
• Component Failure
• Application Failure
• Human Error
• Maintenance
• Site Outage

According to Woon, the geographically dispersed nature of Asian software development means that collaboration and integration tools are vitally important. This is why where ALM tools come into play—making software easy to use and accessible to a wider pool of people, by reducing the complexity and taking the mystery out of delivering large projects.

Erroneous messaging has led many IT managers to believe that clustering applies only to mission critical applications. The truth is that if your organisation cannot tolerate even minutes of planned or unplanned downtime for its business-critical applications, there are powerful high availability solutions within economic reach. They mitigate against the primary threats to the continuity of your business, Woon writes.

Many are the myths and misunderstandings that surround high availability. Typically, they appear as variations on four basic misconceptions, It is costly, it is complicated, it is hard to measure, and it is hard to test. These false impressions persist partly because hardware vendors continue to aggressively press their own agendas.

Software Technologies vs. Availability Threats

Woon reviews the tools that are available for defending the environment against these threats. The most basic availability level is backup to disk or tape—the industry’s fundamental safety net for IT infrastructures. Back up reduces the amount of data loss from data corruption to about 24 hours; depending on how often daily backups are taken.

If your company cannot afford to lose data for that long, the next level of protection against data corruption is local mirroring—creating a constantly updated copy of data on disk to provide real-time availability within the data center, he explains.

When the availability of your data has been established, the next concern is server availability and the protection of business applications. Local clustering technology lets you group several servers into a single resource. Failure on any server results in a failover to another server in the cluster, and availability is protected, reducing downtime to minutes and, in some cases, seconds.

According to Woon, Backups, mirroring, and local clustering can protect you against local threats to availability. But what if the unthinkable happens—a disaster that knocks out your entire site? You can protect your total environment by establishing availability of data and resources at a remote site.

You have two tools at your disposal to accomplish this— replication and clustering.
Replication enables you to create a copy of your data online, in real time, to disk storage at another location. Clustering goes a step further; it combines replication of the application with the data. This means that if you have a complete outage at your primary site, a single button-click will restore service at your back-up environment, he explains.

According to him, the combination of these technologies not only provides 24x7 availability but offers cost savings and Return On Investment (ROI) for IT departments. With that in mind, let’s examine the four myths:

• Myth No. 1: High Availability Costs Too Much
• Myth No. 2: High Availability is Too Complex
• Myth No. 3: It is Too Hard to Measure
• Myth No. 4: It is Too Hard to Test

Knowledge about the use of innovative software technology dispels the myths surrounding high availability. It is much less costly than traditional hardware solutions. It is not complex to manage. In fact, it vastly simplifies management. It can be implemented in minutes, and it can easily be measured, analysed and reported. It puts high availability within easy reach of most companies today.

Read the Article