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In the worlds of finance and manufacturing-process control, every minute a server isn't working costs thousands of dollars. Even mundane applications such as e-mail are critical. It's highly unlikely the designers of the IBM PC ever dreamed that their design would be used for high availability, and yet now it is. RAID and redundant power supplies have been added to plug some of the bigger holes, but hefty cracks remain.
Several software-based assuredavailability systems offer a solution; these usually require specially written applications and some time to start up a new instance of the failed application. Stratus Computer, Sun Microsystems and Tandem (a division of Compaq Computer Corp.). provide hardware-based solutions, but to date none have a Microsoft Windows NT version, though Stratus has plans for a Mercedbased system.
Now, along comes Marathon Technologies' Endurance 4000 to address Windows NT high availability. We had an opportunity to put the Endurance system through its paces and found it to be solid. We liked its simplicity, ease of management and the simple fact that it works. Unfortunately, if you need multiple processors or loadsharing you'll have to look elsewhere (or wait for the symmetric multiprocessing version to arrive). Still, the Endurance 4000 is an excellent solution: Its single processors are fast enough for many jobs and the worry-free system will ease the burden on your IT staff.
Hardware-Software Combo
Endurance is hardware and software designed to combine four personal computers into a single Windows NT server with no single point of hardware failure. And, almost more important to us, the software applications need not be aware that they are running on a high-availability server. In fact, if you're willing to work with an 800 x 600 screen in 16 colors, you could have a high-availability workstation-regular applications work just as they always have.
There are several advantages to
fault tolerance in hardware over software-based systems. Programs don't need modification to be fault-tolerant, which is a substantial advantage for shops with custom applications. The failover time is less than it is with softwarebased failover, and recovery is handled automatically once the failing parts are repaired.
In the Endurance 4000's setup, the computers in the system are divided into pairs, or a tuple in Marathon's lingo. These tuples can...