>>>>> "es" == Eric Schrock <[EMAIL PROTECTED]> writes:
es> I don't think you understand how this works. Imagine two
es> I/Os, just with different sd timeouts and retry logic - that's
es> B_FAILFAST. It's quite simple, and independent of any
es> hardware implementation.
AIUI the main timeout to which we should be subject, at least for
nearline drives, is about 30 seconds long and is decided by the
drive's firmware, not the driver, and can't be negotiated in any way
that's independent of the hardware implementation, although sometimes
there are dependent ways to negotiate it. The driver could also
decide through ``retry logic'' to time out the command sooner, before
the drive completes it, but this won't do much good because the drive
won't accept a second command until ITS timeout expires.
which leads to the second problem, that we're talking about timeouts
for individual I/O's, not marking whole devices. A ``fast'' timeout
of even 1 second could cause a 100- or 1000-fold decrease in
performance, which could end up being equivalent to a freeze depending
on the type of load on the filesystem.
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