Poor read performance with Windows 7 x64 from Celerra CIFS

Hi,

We are experiencing poor read speeds (<2MB/s, sometimes <768Kbps) from a CIFS share on our Celerras when accessed from some Windows 7 SP1 x64 clients. Other clients, generally 32 bit Windows 7 SP1 or Windows XP do not experience the issue, even when on the same VLAN as clients which do have the issue. Uploads to the CIFS from the same clients work fine and will easily hit 10MB/s.

The clients and Celerras are in different subnets. We have tried numerous solutions, some of which work on some clients but not all. Some of the solutions we have tried are as follows:

Upgraded NIC Drivers

Disabled IPv6

Disabled/changed varying netsh interface tcp global options

Imported netsh dump from working machine after applying netsh interface tcp set global autotuninglevel=disabled

Disabled Remote Differential Compression

Disabled NetBIOS over TCP (Although it still seems to use TCP)

Disabled SMB2 (this caused a slight improvement but not much)

A packet capture shows a significant number of Delayed ACKs returned from the clients to the Celerras and numerous retransmits from the Celerras. There are also out-of-order packets.

Our Celerra NAS Code is 6.0.65-2. This occurs with two different Celerras.

Our PCs are standard Intel based motherboards (e.g. Intel DQ67) with Intel based NICs (e.g. Intel 82579LM Gigabit Network).

I have attached my netsh dump.

Any help would be greatly appreciated.

Thanks,

Tom