Very bad performance when copying large files from windows to samba-share

Esh, Andrew AEsh at
Fri Apr 12 10:53:02 GMT 2002

Yes, it's the "rabbit pellet" problem. I just gave him the IP problem
breaker because it was the easiest to test. There's actually six conditions:

 1. The client must be Windows 98 (not Windows NT).
 2. The server must be Samba (not Windows NT).
 3. The Samba server must be in "security = server" mode (not share or
 domain mode)
 4. The file being transferred must be uploaded (not downloaded).
 5. The file must be transferred by the Windows explorer (not a command
 line copy).
 6. The drive must have been mapped by name (not by IP address).

This isn't his problem.

-----Original Message-----
From: Christopher R. Hertel [mailto:crh at]
Sent: Friday, April 12, 2002 12:10 PM
To: Esh, Andrew
Cc: 'Lars Heineken'; samba-technical at
Subject: Re: Very bad performance when copying large files from windows
to samba-share

> "Esh, Andrew" wrote:
> I also have a lot of experience with Win98. There is a performance
> problem which is difficult to produce, but large files should still
> be copied, albeit slowly. To avoid the performance problem I am
> speaking of, make sure you mount the share using the IP address of
> the host, and not its name.

Is this the 'rabbit pellet' transfer we dug into a while back?
If so, using security=server should also be avoided to avoid the

The problem in this case (for the rest of our viewers) is that Windows
Explorer (the GUI) detects subtle timing delays and will slow itself
down.  It sends the file using small packets, sends a flush after each
packet, and requires an ACK after each write and each flush.

If this is the behavior that is being seen then I don't think we have a
solution for it other than avoiding security=server and, as Andrew
explained above, connecting to the share using the IP address.  You
could also shake bones and burn tana leaves...  It's a wierd problem.

Microsoft did put out a fix for this...but those who tried it had worse
results.  I can't seem to find the KB article any more, but if I recall
correctly it said that the change to using small packets with a flush in
between was to accomodate network links via satellite.  (!?)

Chris -)-----

Christopher R. Hertel -)-----                   University of Minnesota
crh at              Networking and Telecommunications Services
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