[OpenAFS] Windows client network behaviour
Wed, 21 Sep 2011 13:09:26 +0200
In the hunt for oddities regarding the new IFS Windows client I have
observed a problem causing bad performance, and hopefully someone has
some idea about what is going on.
Server: OpenAFS 22.214.171.124, CentOS 5.3
Client: Windows 7, OpenAFS 1.7.1
The test case is to write an ISO image (700MB) to afs from local disk.
If the switch port is set to 100Mbit I will get ~3Mbyte/s, but if it is
set to 1Gbit then I get ~10Mbyte/s.
Both these numbers are much lower than they should be, and more
precisely I cannot understand why the speed in 100Mbit configuration
becomes much lower than when using 1Gbit.
Before someone asks; there are no network limits here and both client
and server are on the same subnet.
I have run tcpdump on both client and server and seen this traffic
- A data packet is sent out periodically at an almost exact rate of one
per 420 microseconds, which gives something close to 3Mbyte/s
- The same as for 100Mbit except for that the packet rate is one packet
per 91 microseconds.
The ack packet from the file server is sent back 12 microseconds after
each second data packet.
I have uninstalled the QoS module on the Windows interface.
Any hints anyone? I think this smells as traffic shaping due to the
quite exact transmit rate but
since the QoS module is uninstalled and the behaviour is seen on the
windows network interface
I have no clue where it may be.
A side note: Going via a SMB-AFS gateway on the same network gives