Reduced write performance for Riverbed WAN links when working with AutoCAD MEP 2007 DWG files

In March 2006, Autodesk changed the DWG file format for AutoCAD 2007 to make it more compact and improve performance for AutoCAD users. Autodesk’s customers widely welcomed this change and almost all AutoCAD users have enjoyed improved performance.However, Autodesk and Riverbed have recently received reports that some customers using some WAN acceleration appliances, including Riverbed’s Steelhead appliances, have experienced noticeable reductions in write performance when working with files saved in the AutoCAD 2007 “DWG” format. One of the side effects of the DWG format changes is that when users perform a complete save from within AutoCAD (as opposed to an “incremental” save), virtually every byte of the file gets changed – even if zero changes were made to the file itself. The net effect is that writes that would normally affect only “warm” data are actually “cold”, due to the reordering of the data in the file.Users of Riverbed or other affected WAN acceleration solutions can implement the following immediate workarounds that improve write productivity.

1. Using a feature in AutoCAD called “Incremental Save Percentage” (ISP), and setting it to 50
2. Using a version of the DWG format other than the AutoCAD 2007 DWG format.

The performance and productivity of their customers is a key consideration for Autodesk and Riverbed. Both engineering teams are working together to devise workarounds and are examining potential longer-term solutions. Given Riverbed’s experience in WAN acceleration technology, our joint work may also provide solutions for customers of other WAN acceleration or deduplication technologies, who might be experiencing similar issues with write performance.