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Correction... we have both Ontap 6.4.2 and 6.5.1p1 running... both FAS960s have CIFS latency issues. And we have an open case w/ Netapp...

We're experiencing severe latency when a Windows 2000pro or Windows XP client reads and writes to a folder on our Netapps (FAS960 w/ Data Ontap 6.5.1). It only seems to be client O/S as our testing w/ a Windows 2000 Server did not have latency on reads / writes.

We're currently looking at SACK and TCP Window sizes. Has anyone experienced severe client latency? Any know issues / advice? Anyone changing the sack option on their Filers?

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SackOpts

This parameter controls whether or not SACK (Selective Acknowledgement) support is enabled, as specified in RFC 2018. SACK is especially important for connections using large TCP Window sizes.

HKLM\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters

SackOpts="1" (DWORD - boolean, recommended setting is 1. Possible settings are 0 - No Sack options or 1 - Sack Option enabled).

http://www.speedguide.net/read_articles.php?id=157

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One more item of note. In the traces from the slow xp box, we're showing a boatload of SACK transmissions, whereas in the fast one, not a one. I'd like to turn off SACK on the filer side to see if things clear up or not as google isn't giving me much luck in the 'which registry entry do I change to check things on the windows box' angle.

On the filer:

filer> options ip.tcp.sack.enable off