Fault tolerant server maker Stratus Technologies today said it is now supporting VMware's entry Infrastructure 3 Foundation and midrange Standard editions running in conjunction with its ftServer boxes. Stratus is one of the pioneers - along with Tandem (now part of Hewlett-Packard) - in fault tolerant servers. With fault …
"With fault tolerant architectures, server components are doubled up and cross-coupled in such a way as to present a single image to end users, with the two duplicate systems running in absolute lockstep."
That's a fair description of the way Stratus provides a fault-tolerant hardware platform. Tandem's approach is more software based, with keep alive messages between duplicate software instances allowing seamless takeover from a failed process. No lock-stepped CPUs are involved.
There are advantages and disadvantages to each. It's more difficult to port third party apps to a Tandem platform, but OTOH software is a much more frequent cause of system failures than is hardware.
Re: Not quite
I believe that the observation "Tandem's approach is more software based, with keep alive messages between duplicate software instances allowing seamless takeover from a failed process. No lock-stepped CPUs are involved." is not quite right.
Tandem does use lock-stepped processors; a pair forms a single 'self-checked' processor. Each of the primary and secondary processes (forming a duplicate software unit with keep alive messages etc ) runs on a distinct 'self-checked' processor.
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