ONTAP Hardware

CIFS upload performance issues over WAN


Hi there,

I'm experiencing some really weird performance issues with CIFS over a WAN connection between two of my sites.

Site A - FAS2040 + Windows File Servers

Site B - Windows File Servers

Connected via MPLS - 70Mbit

When copying files via CIFS I'm seeing the following:

B downloading from A - FIle Servers > 7MB/sec

B downloading from A - FAS >  7MB/sec

B uploading to A - File Servers > 7MB/sec

B uploading to A - FAS > 1.75MB/sec

B uploading to A - FAS via FTP > 7MB/sec

Performance in Site A is fine, when uploading to the FAS. File servers and FAS are on the same VLAN in Site A

Scratching my head over this one so hoping someone can nudge me in the right direction, have checked everything I can think of...wondering if its some sort of duplexing issue.

Thanks a lot



Hi, just to update, this was fully resolved by increasing the cifs TCP window size from 17520 (default) to 64240 and restarting cifs. Happy days!



View solution in original post



Whats your testing platform on the client?

If it is Windows XP/2003 or older then you are running SMB1.0 protocol which is known to work terrible on WAN.

If you are testing with Windows Vista/2008 or newer then check that SMB2.0 protocol is enabled on your FAS.

Also, Vista/2008 and newer has a better TCP stack which might help get some more performance with SMB1 if you might need to stick to it.



Besides what the other post said, what have you tried?

Try reading up on the 'netdiag' and 'ifstat' commands on your NetApp.

How long is the WAN connection?  ... in milliseconds...   The TCP window size for SMB 1.0 typically very small, so high-latency links will suffer a lot more.  You can manipulate the filer side with the option cifs.tcp_window_size (17520 is the default) but I am not sure it is going to help or not.  SMB 1.0 is just broken.  Read up on calculating window sizes for TCP connections.  YMMV.

Check your switchports if you are seeing collisions in the ifstat output.

By the way, 7MB/s is still over 55Mbit/s, so you aren't doing too badly if the link is shared with other traffic.


Hi thanks for the responses.

The FAS is already set to SMB 2.0 and the clients I'm testing from are Windows 7 and 2k8R2. cifs sessions command confirms the active sessions are running via SMB2.

Wan link is ~10ms so no issues with latency.

Have checked ifstat on the FAS interfaces and they show zero collisions.

netdiag pops a couple of warnings about NFS TCP packet sizes being slightly off (these are on seperate interfaces to CIFS though) I'll take a look at fixing these in the meantime.

To clarify, I'm more than happy with the general 7MB/sec performance, it's just uploading from SITE B to A that is the issue. It refuses to transfer to the FAS faster than about 1.75MB/sec, as if its capped somehow, whereas uploading to 2k8 servers in SITE A is fine.

Checked routing and it all seems to be fine.

FTP traffic uploads at the full whack, just seems to be CIFS thats affected.

Any other suggestions welcome, I'll keep plugging away at this.



Hi, just to update, this was fully resolved by increasing the cifs TCP window size from 17520 (default) to 64240 and restarting cifs. Happy days!