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SubjectRe: NFS client problems in 2.4.18 to 2.4.20
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>>>>> " " == Jamie Lokier <jamie@shareable.org> writes:

>> This is not an issue for tapes, etc. NFS has an alternative
>> mechanisms for dealing with this in the form of the
>> NFSERR_JUKEBOX error.

> Oh, cool. Perhaps the server should send these automatically,
> when I/O operations are taking a little bit too long?

Yes. Needs a patch to knfsd, but would be very useful for people that
want to export tapes, CD exchangers, etc...

>> By setting 'retrans=6' (5 + 1 to compensate for the bug),
>> therefore, people can ensure that we retry for at least 6
>> seconds before timing out. The question is: is this an adequate
>> default?

> That would be a big improvement. I take it you have
> effectively clamped the retransmit time at a minimum of 1/10
> second, then? (I didn't understand what you meant earlier).

Yes. When we calculate the timeout value, we add the estimated error*4
to the estimated round trip time. I've set a floor on the former value
so that the minumum timeout will be 1/10second.

> Last time I used a soft mount, I was seeing the first
> retransmit after some time smaller than a millisecond. (I
> don't remember, but 0.1ms sounds about right). If that is the
> retransmit time, then retrans=6 won't be enough - retrans=16
> would be needed. I don't think a good correct retrans=xxx
> setting should depend on the network like that. Setting a
> minimum retransmit time is one way to fix that.

It is already in 2.6.0. I'm expecting to put it into 2.4.23 too, but I
want to know that this (together with a patch to 'mount' to change the
retrans default) really does solve the problem for people...

Cheers,
Trond
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