While investigating rsync/ssh performance, I discovered that our Solaris Clusters had just over half the expected throughput on their gigabit NICs.

This was caused by the cluster/streams related module clhbsndr being automatically pushed to each public NIC via /etc/iu.ap .


  • Round trip time via ping was higher than non-cluster servers on the same network
  • The throughput measured with iperf (and other tools) was around 400-600MBit/s instead of 940Mbit/s
  • The clhbsndr module is loaded for the public interfaces, eg
ifconfig e1000g1 modlist

0 arp
1 ip
2 clhbsndr
3 e1000g


We have confirmed that bug 6625886 is the cause and are now waiting for Oracle to say if the module can safely be removed from the public interfaces of a Solaris 10 cluster, eg:

ifconfig e1000g1 modremove clhbsndr@2

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