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LCA: Andrew Tanenbaum on creating reliable systemsLCA: Andrew Tanenbaum on creating reliable systemsPosted Jan 18, 2007 18:23 UTC (Thu) by emkey (guest, #144)In reply to: LCA: Andrew Tanenbaum on creating reliable systems by oak Parent article: LCA: Andrew Tanenbaum on creating reliable systems
Making a system fault tolerant would in theory mask all bugs. Fixing a bug fixes ONE bug. Thus fault tolerance is a much better short to mid term investment. Also, debugging problems is potentially much easier in the fault tolerant model. For example, many bugs can cause a system to become unresponsive. It is thus nearly impossible to gather data that might help in identifying and solving the problem. With a fault tolerant system you could optionally enter some sort of debugging environment when a particular component failed. This could greatly reduce the amount of time needed to fix problems.
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LCA: Andrew Tanenbaum on creating reliable systems Posted Jan 18, 2007 18:55 UTC (Thu) by oak (subscriber, #2786) [Link] Good points, but I've seen "fault tolerance" implementations whichmake the system less responsive[1] and/or obliterate the traces of the actual fault[2]. :-) [1] Windows virus scanning software repeatedly starting some crashing service so that opening any application window takes >20 minutes [2] Linux SW restarting the crashed service which act changes the system HW state that caused the original crash and results in a different crash. You could fix the constant service restarts only by examining the HW state for the first fault So, I would say that if fault tolerance is done, great care would need to be taken that it will really help also in finding and fixing the bugs (by notifying user about the fault, saving data about the fault state, allowing debugging of the fault when it happens etc), not just hiding them. And this code should be fairly simple to assure that it actually works, more complicated code is always harder to maintain and usually contains more bugs...
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