Desktops
Don't overlook the desktop or notebook computers used by your staff to access critical systems. If you have a standard configuration and operating environment, it is relatively easy to plug in a replacement system in the event of an isolated failure. The faulty equipment can then be repaired at leisure.
But what happens in a disaster situation when hundreds or thousands of units need to be replaced simultaneously? Sourcing and installing that many units is hard enough--especially in temporary premises--but what about loading all that software on each of them? One way around this problem is to deploy critical applications via Citrix servers.
Navin Rajapakse, assistant vice president at Lehman Brothers, says that when the company lost its New York office in the September 11 attack on the World Trade Centre, temporary workplaces had to be found for 7000 employees.
Two thousand traders were relocated to a temporary site in New Jersey, but the remaining 5000 staff worked from hotel rooms, home, or other temporary offices and relied on the Internet to access IT resources.
While Compaq and Sun quickly provided the company with replacement servers after September 11 and IBM did the same with 5000 notebooks (the dot-com bust meant there was plenty of hardware inventory around the country), Rajapakse says there wasn't time to load a standardised system image on each computer, so they just installed the Citrix client and ran the applications on the servers.
This approach was successful, and the company plans to retain the facility for ongoing remote access purposes. According to Rajapakse, Lehmann Brothers is still investing in disaster preparation but wants to be able to make use of its investment during normal operations, for example by using it to deliver applications to clients. "We're trying to make the best use of our infrastructure," he says.
Software
Software is said to be the major cause of downtime. Marcus and Stern point out that the increasing reliability of hardware coupled with technologies that reduce planned downtime means software-related downtime is set to rise proportionately.
Software is growing more complex, and all other things being equal, that is likely to reduce reliability. The question is whether improvements in software development, debugging, and testing are sufficient to decrease software-related downtime.
High-availability hardware can be an expensive way of protecting against buggy software. It may not even be effective: if failover occurs when a buggy program encounters a certain value in a particular data field (eg, attempting to divide by zero with no error trapping), the secondary system will be brought to a halt by the same bug.
Modern applications rely on multiple software layers. To achieve high availability from the end-user's perspective, they all need to be running. Even a relatively simple architecture may involve a server operating system, database, application, network routing, PC operating system, web browser, and a Java applet.
While most organisations would regard their ERP or accounting systems as business critical, it is important to examine the entire software portfolio to see what is essential to that particular environment. "Many companies could not operate without e-mail," says Wissam Raffoul, senior program director, service management strategies at META Group.
It's not only e-mail: a consulting firm could be completely paralysed without its Exchange or Notes server. Staff wouldn't know which client they were supposed to be attending, where and when meetings were being held, and so on.
Another important consideration is the nature of dependencies between systems. Once a particular application is defined as critical, all the systems and subsystems it relies on must also be considered critical.
For example, a short-term capacity problem might result in a certain database being deployed on what was notionally a development server. If that data is used by a critical application, the health of the development server has suddenly become business-critical as well.
