• GET INFORMED • • • • • • Designing a Fault Resilient Phone System by Brian McConnell One of the greatest benefits of owning a PC-based telephony server (besides the extra features they offer) is the freedom to decide how to plan for and how much to spend on fault tolerance. Your telephone system is obviously one of the most important parts of your business. Yet, the vast majority of business owners have little or no idea how their phone systems work, and how to fix them when something goes wrong. PC-based systems, if designed and managed properly, can be made as reliable, if not more so, than the most expensive proprietary phone systems on the market.

For a number of reasons: • PC technology has advanced considerably in recent years, with advances in both operating systems (such as Windows NT) and fault tolerant components (such as Redundant Array of Inexpensive Disks, or RAID). • PC-based telephony servers are largely composed of generic components which can be quickly and cheaply replaced. • These systems can often be managed by somebody in house, meaning the response time when a component fails is the length of time it takes this person to walk across the office. When you look at the overall picture, including the reliability of the components, availability of low-cost spare parts, and ease of use and maintenance, these systems give traditional systems a serious run for their money. This article explains how, using some common sense rules and fault tolerant technologies, you can create your own telephony server which will be as reliable as the most expensive proprietary system on the market.

This article can be considered two separate articles, one on fault tolerance (i.e., designing a system so it won't fail), the other on disaster preparedness (i.e., mapping a strategy for responding quickly to a system failure). The first, and most important thing to understand is that no system is 100% reliable. Segger J Flash Arm Keygenguru there. This is a simple fact of human existence. Something is always screwed up somewhere in any reasonably complex system. If you believe any vendor who promises that their system will 'never fail,' I'd be glad to sell you the Golden Gate Bridge for $50,000 (offer expires April 1st).

Fault tolerance (designing systems to fail gracefully) Your body is an excellent example of fault tolerant design. Throughout your body, you'll find redundancy everywhere.

Fault Resilient Drivers For Longhorn Servers. Fault resilient device drivers. It provides the application program interface. Fault Resilient Drivers For Longhorn Server Salary. Selling server tools as a separate downloadable application through the Mac App Store.

Redundancy is the key to fault tolerance. The basic idea behind redundancy is a simple one. For any system which is critical, always have one or more backups which can take over if it fails. PCs are built using many different low-cost components. Some of these components are not critical (i.e., if they fail, the system will continue to function. A floppy drive is a good example of this type of component. Others (i.e., CPU, hard drive, power supply) are critical to the continued operation of a server.

PC components can be divided into two general categories: components with moving parts, and components without moving parts. Solid state components such as memory, the CPU and other circuitry are statistically much less likely to fail (provided the server is properly protected from power supply fluctuations) than moving parts such as disk drives and power supply fans. Of all the components in a typical server, there are a few which are most likely to fail: the power supply, hard disk drives, and CPU fans. Solid state components can still fail, but if the server is protected from external power surges and extreme environmental conditions, this is not likely to occur. Fault tolerant storage media (RAID arrays) A hard disk crash is every system administrator's worst nightmare. Restoring hundreds of megabytes of data from tape is a time-consuming task.

Better to avoid a crash altogether. RAID arrays provide an excellent fault tolerant storage medium for small and large servers. A RAID array operates on a simple principle. Rather than saving data in one location on one disk, a RAID array stores data in many locations on many disks. So, when a drive in a RAID array consisting of 10 disks fails, the array as a whole continues functioning. The faulty unit can be swapped out with no disruption to users, and so a formerly nightmarish occurrence becomes a non-eventful maintenance task. NOTE: Most of the high-end PC operating systems such as Windows NT, OS/2, NetWare, and UNIX support RAID arrays.