suggested ways of faking EIO?

Julian Elischer julian at
Sat Nov 24 01:12:44 PST 2007

Dan Nelson wrote:
> In the last episode (Nov 23), Julian Elischer said:
>> I need to make physio make a request from disk, and have the request
>> come back asynchronously with an EIO. 
>> I have tried just reading some distance past the end of a partition,
>> but I'm not totally convinced that it acts exactly like as if I'd
>> tried to read a bad sector. Since geom has been added, the legality
>> of a read needs to be tested in the geometry layer, so I suppose it
>> must come back asynchronously, as that is no longer directly executed
>> through function calls but is it really the same as a disk failure?
>> Anyone done this? or does anyone have a disk with a known bad sector
>> I can try my test case on? :-)
> The geom NOP module can fail a given percentage of I/O with whatever
> error number you choose.  You could hack g_nop.c to make it fail on a
> given sector instead.

great! that's the hint I'm looking for...
(now to work out how to use it)

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