[Samba] Marginal write performance & pauses in outgoing transfers - Possible bug

[Joseph Healy]

Hi,

We have been seeing similar symptoms on win98 clients with canon printer
monitors (LBP-810).

Having the monitor running seemed to cause the smb requests to go in
bursts with delays of about one second between groups. Removing it
solved the problem. Caused big problems myob premier and large datafiles
(130mb).


Probably unlikely but it drove me crazy for well over a week.

Joe



On Sat, 2003-07-26 at 23:36, Nicolas Gieczewski wrote:
> Hello everybody,
> 
> I have a FreeBSD 4.8-STABLE server running Samba 2.2.8a and a workstation
> running Windows 2000 SP4. Whereas FTP transfers between these boxes average
> 700 KB/s (10 mbps LAN) in both directions, Samba transfers are exhibiting
> this odd behavior:
> 
> Windows 2000 --> Samba = 700 KB/s (perfect)
> Samba --> Windows 2000 = 100 KB/s (terrible, inconsistent, with LONG pauses)
> 
> Trust me, I have tried *everything* I've run into as far as tuning goes,
> so please don't ask if I've tuned up my stuff or request my configuration
> file :)  If this were a configuration-related issue, performance should be
> the same no matter in which direction data is transferred. Nevertheless,
> I have really tried everything that exists. Furthermore, I remember I didn't
> have this problem with certain older version of Samba before I upgraded
> my ports (unfortunately I don't remember which version it was, but I don't
> really want to downgrade).
> 
> The problem lies in the fact that outgoing transfers are not consistent and
> undergo VERY long, random pauses. My hub's activity LED shows that, during
> a transfer from Samba to Win2k, no packets are transferred about 70% of the
> time. Yep, only during about 30% of the total time a transfer takes is there
> actual network activity--the remaining 70% of the time is wasted on random
> (both length-and interval-wise) pauses. When transferring the other way
> around, though (Win2k --> Samba), it's just as fast as FTP (because I *do*
> have my stuff properly tuned!), so fast in fact that it makes my hub's
> excessive bandwidth alert LED go on ;)
> 
> All my network cards are propery configured, both media- and duplex- wise.
> There are no collissions. I don't even know why I'm saying this, because the
> rates I can achieve with FTP both ways alone proves that Samba is the
> culprit.
> 
> Because most of the time a transfer takes to complete is wasted on those
> random pauses, anything I could tune concerning buffer sizes and the like is
> almost useless because it only takes effect while data is actually being
> transferred, not during the pauses. I have fiddled with buffer sizes and, by
> looking at the hub's activity light, I could (visually and easily) see how
> more or less data was transferred in between the pauses depending on the
> buffer sizes I chose. However, the pauses stayed consistent throughout all
> my tests. By using larger buffer sizes, all I could do was push more data
> through in between the pauses, but my tuning never affected the length or
> interval of the pauses themselves. Buffer sizes are not the only thing I
> fiddled with, and anyway, this was the same configuration file I had been
> using with that older version of Samba that didn't have this problem, and
> nothing changed in between.
> 
> And again, the pretty good rate (for a 10 mbps LAN) I can achieve in
> the Win2k --> Samba scenario proves that there's nothing wrong with
> my configuration.
> 
> Does anyone happen to know what could be causing this? I ran into a post
> on the FreeBSD net mailing list posted a long time ago by someone who had
> this same problem, but his difference between read and write performance
> was much bigger, and that was an ancient version of Samba which had
> certain wait flag turned on in the code. However, that was supposed to be
> off by default in future versions.
> 
> Please advice!
> 
> Thanks in advance,
> 
> Nicolas Gieczewski
> Nix Software Solutions
> http://www.nixsoftware.com/
> 
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