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I have a IBM N-series 3700 (NetApp Filer) running data ontap 7.4. When I run netdiag I get:

The TCP receive window advertised by NFS client x.x.x.x is 5888. This is less than the recommended value of 32768 bytes. You should increase the TCP receive buffer size for NFS on the client. Press enter to continue

Average size of NFS TCP packets received from host: x.x.x.x is 969. This is less than the MTU (1500 bytes) of the interface involved in the data transfer. The maximum segment size being used by TCP for this host is: 1460. Low average size of packets received by this system might be because of a misconfigured client system, or a poorly written client application. Press enter to continue

The clients are RHEL 5.5 and both the filer and clients are on the same switch. I was going to install ktuned to help with the tuning. Any other suggestions?

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Have you read about the option "ip.path_mtu_discovery.enable", if your switches support this, as well as the RHEL boxes it might be worthwhile to experiment with.

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