It's not uncommon for alcoholics to suffer from the DT's (Delirium Tremens — severe alcohol withdrawal characterized by agitation, violence, anxiety, insomnia, muscle cramps, tremor, delusion, hallucinations, and fever). But whoever heard of an operating system (OS) suffering from the malady? Well, the OpenVMS OS apparently has an acute case of the DT's. Though in this instance, we are talking about disaster recovery.

Disaster Tolerance (DT) is a concept that extends beyond disaster recovery (DR). Traditional DR focuses on minimizing downtime then picking up the pieces and reconstructing any lost data afterwards.

DT, on the other hand, has the goal of continuing to operate despite a disaster so bad as to result in total destruction of an entire datacenter. This is made possible by placing servers and storage at each of two (or more) sites that are separated geographically by a safe distance. Essentially you have to keep the contents of that storage identical at each of the sites at all times.

Expensive? Yes. But if an hour of downtime costs you millions of dollars, or could result in loss of life, the price is worth paying.

That's why big companies in healthcare (Dartmouth-Hitchcock Medical Center, and Cerner and IDX, who write software for hospitals), transportation (Fraport AG is the Frankfurt airport), finance (Bank Austria Creditanstalt and Commerzbank), as well as manufacturing and government are willing to spend big to achieve disaster tolerance. And OpenVMS is the OS of choice when it comes to disaster-tolerant clusters.

"You will find OpenVMS in any environment that is serious about high availability, disaster tolerance, security, performance and scalability, especially when running real time or near real time applications," said Colin Butcher, an analyst at UK-based research firm XDelta limited.

An early example of the effectiveness of OpenVMS is DT came in the mid-nineties in Paris when Credit Lyonnais survived a fire at its headquarters. Its multi-site OpenVMS Cluster safely mirrored its data at a second site, while the UNIX folks reportedly had to run into the burning building to pull the most-recent backup tape cartridges containing their data from the tape drives.

The big test of Disaster-Tolerant OpenVMS clusters, however, came on 9/11. At least seven big financial services companies (including Cantor Fitzgerald and Commerzbank) avoided an IT collapse by using the OS for DT.

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