REPOST: Performance problems with FTP

[Charles Swiger]

On Jun 29, 2004, at 3:38 PM, Bill Moran wrote:
> Charles Swiger <cswiger at mac.com> wrote:
>> I haven't seen any signs of such problems with 4.10.  Given that 
>> you've
>> reproduced this using different FTP servers, it seems more likely to 
>> be
>> a network issue or some hardware glitch (cables? flaky NIC?) than a
>> software issue.
>
> I hadn't even considered hardware, becuase scp is always as fast as I
> would expect.  I wouldn't suspect a NIC or HDD, unless the problem was
> consistent with _all_ file transfers, and it's not.  The performance
> issue only occurs with FTP.  If I'm wrong on this, I'd be happy to hear
> about it, though.

You're not wrong, and I don't see anything obviously wrong, so I'm 
reaching for possibilities to check.  :-)

>> Can you reproduce by moving ftp to a different port #?  (Perhaps some
>> quality-of-service thingy is providing different bandwidth by port...)
>
> I haven't tried that, but I forgot to mention that a Debian box located
> right next to the problem box (on the same network) gets speeds equal
> to what would be expected.  To me, that ruled out QOS, routing and 
> other
> beyond-my-control Internet problems.  Again, I'm happy to be corrected
> if there's something here I'm not aware of.

Well, that does tend to rule out a bunch of issues.  Have you tried 
changing the MTU of the FreeBSD box down to 1400 or so (or even 512), 
just to see whether that does anything?

> This is just a snippet ... but it looks like an awful lot of 
> retransmits
> and duplicates to me.  I hadn't looked at this before, is this 
> indicative
> of any particular problem?

You're seeing ~1% or less retransmits, that's pretty normal.

-- 
-Chuck