How to debug 100x variance in writing the same file?

[Richard Sharpe]

On Fri, 21 Jan 2005, Christopher R. Hertel wrote:

> The problem we are suggesting *may* be the source of your headache is the
> request/response nature of the higher-level SMB protocol.
>
> With a stream protocol, if a packet is dropped it is simply resent a few
> packets later and the receiving end pops it back into its correct place
> and all is well.  Other packets continue to flow so there is little
> interruption.
>
> With a request/response protocol, if a packet is dropped the entire
> transaction gets held up.  You have to wait until the timeout expires
> before the dropped packet is resent, then the transaction is processed,
> then the response is sent and, once again, if you lose a packet you wait.

OK, to be more specific, if a packet is dropped towards the end of a
read response (or a write request) where there are no subsequent segments
to trigger normal TCP behavior (fast-retransmit) then we will see big
reductions in throughput as Chris mentions.

Regards
-----
Richard Sharpe, rsharpe[at]richardsharpe.com, rsharpe[at]samba.org,
sharpe[at]ethereal.com, http://www.richardsharpe.com