isilon smb performance over wan

hello,

We've been wrestling with isilon poor smb performance in field offices over wan connections, it's over a wide variety of connections including mpls, cable, vpn etc so it's not the connection, a traffic, congestion or saturation issue and other protocols over the same links work without issue, it's almost exclusive to smb. Which is already bad over wan but isilon performance with smb is worse than other systems.

The major pain points with smb performance over wan is when opening or saving large word, excel and pdf files. Saving a pdf file containing multimedia including pictures, text, etc that's a few mb can take up to a few minutes. Performance declines the deeper into a share file structure the file resides.

Initially, this was an issue with smb oplocks being turned off to satisfy some application performance issue, turning it back on relieved some but not all the performance issues.

We've looked at tuning the tcp window on isilon, but were told those are typically no modified on isilon because it could "cause issues." And, it's a "design decision."  

What other parameters or configuration on the isilon could we tune to improve smb performance over wan? I've read we could optimize smartconnect to pin clients to one node so they don't hope from node to node reading/writing files from the same smb share. Also we could look for metadata, ACL enumeration, tree enumeration issues that could also impact SMB.

Please comment and provide suggestions!