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I've got an Xserve3,1 running 10.6.8 server, that hosts home directories for some of our students and it seems that whenever AFP connections approaches 280 or higher, performance drops dramatically. Student's can't log in, or students that are logged in can't save work. The home folders are stored in a fiber channel SAN (50% full) so I know that the storage isn't the bottleneck. The server has 24 GB RAM, 20 of which is Free or Inactive most of the time. When I disconnect sleeping accounts or restart AFP or the machine itself (basically anything that gets the number of connections back down to under 720) performance returns to normal.



Does anybody know what else could be causing this issue?



Here's a picture of the Activity Monitor on this server with about 230 users connected.
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img tags are case-sensitive apparently.



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Just some quick hits:




  1. What is your network backbone (connectivity to server, etc.)? What are you using?

  2. I assume storage is direct connect? How long since the last reconfigure / reformat, etc.?

  3. Is the server or clients bound to AD, OD, NIS?

  4. Why 10.6.8? Any folder redirection? Automounts? Kerberos working? True network homes or syncing or both?

  5. Any NAT issues? Wireless / off-site? VPN? L3 switch or no?

  6. What OS are the clients running?

  7. What other service are running on this box? Can you verify DNS forward and reverse?

  8. How long since the OS was reinstalled / refreshed?

  9. Using SMB or NFS as well?



Not all are determinative, nor exhaustive - but would give everyone a better idea of the environment.

I had a similar issue after upgrading a 10.4 server to 10.5 in 2008. The solution for me (which I now use as standard practice) was to increase the AFP MaxThreads value to 600. To do so, run the following Terminal command: serveradmin settings afp:maxThreads=600



Then restart AFP.



This allows AFP to better utilize available RAM and CPU cycles.

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