Re:Real System Failures
by nickpsecurity on Friday July 14, 2017 @08:25AM
(#14769206)
Many of us in high-assurance systems have witnessed triple, modular redundancy fail. I started saying 3 out of 5 for that reason. May be same for other commenter. I also want where possible for the computers to be in different locations, using different hardware, and with different developers working against same API.
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Yes, but those aren't Byzantine failures. Byzantine failures present with incorrect values, not simply the absence of a value (as seen by a total hardware failure).
See the abstract in Lamport's original paper introducing the Byzantine generals problem [0].
We also see a similar issue in error correction -- an introductory undergrad course might teach this via Lagrange interpolation [1], where you need only n+k of the coefficients in the presence of erasure errors, but n+2k in the general case (where n is the size of the actual message, and k is the maximum number of errors to correct).
[0] https://www.microsoft.com/en-us/research/wp-content/uploads/...
Re:Real System Failures
by nickpsecurity on Friday July 14, 2017 @08:57AM
(#14769413)
Partial hardware failures exist. The wrong values start going through the system. A bit flip is easiest example. NonStop has been countering both partial and total HW failures in their design a long time now.