I've been trying to back up an OS 9 laptop without any writable media, and that includes the System Folder. The easiest way to do this would be to boot from CD and Appletalk things to someplace with enough room for the backup. Well, when one Appletalks from OS 9 to OS X as a server, they're likely to get the error, "The file server's connection has unexpectedly closed down."

Guess what happens next? Yep, the Appletalked OS X share drops off of the OS 9 desktop.

Apparently this happens when you try to copy a file over a certain size across the Appletalk connection. I've seen complaints of this happening with as small as 500k.

Luckily, this Apple help file has an answer not only for OS X Server, but also for plain jane OS X trying to share with OS 9. You have to use the "defaults method".

Solution

On the server, change the TCPQuantum value used by the Apple File Service from 262144 to 327680. You can change this value using the serveradmin command, or by directly editing the preference file. You only need to use one of these methods:

[ignore OS X Server-only method]

defaults method

Make sure all users are disconnected from the server.
Stop Apple File Service.
Open Terminal (or ssh to the server from another computer) and execute this command on a single line:
sudo defaults write /Library/Preferences/com.apple.AppleFileServer TCPQuantum -int 327680

The end. Instant giant file transfer via Appletalk. Thank freakin' heavens. That was annoying.