We have a Dell PE2950 file server running Windows 2008, hosting a DFS namespace of ~1.2 TB. This server has two Broadcom 1Gbps NICs teamed together.
When there is high traffic going to the server across the network (greater than 200 Mbps), any Windows 7 client accessing a DFS share at the time experiences severe performance problems.
- Computer A has an AutoCAD drawing opened directly from the DFS share. Performance is normal, not causing any issues.
- Computer B begins a file transfer, putting a 11GB file onto a different DFS namespace, on the same server
- Computer A immediately notices lag while using AutoCAD. The cursor momentarily freezes within AutoCAD every 10 seconds or so, and any browsing of the DFS share is extremely slow.
- Computer B completes file transfer, and performance resumes to normal for Computer A.
This is only affecting Windows 7 clients, using a variety of hardware (desktop + laptop). All of our Windows XP clients see no performance impact during the file transfer.
Things I have tried with no change:
- Had Computer A work from an entirely different RAID array from the file transfer destination
- Updated NIC drivers on clients and server
- Enabled TCP offload and receive side scaling on the server NIC (previously disabled when the issue began)
- Antivirus disabled during file transfer
I am currently having a user test applications other than AutoCAD when the file transfer occurs, and will update the question with that result.
Does anyone have any recommendations for resolution or additional troubleshooting steps?
Update: This issue appears to only affect Windows Explorer and AutoCAD. Using a separate application such as Microsoft Office or Internet Explorer (to an intranet page on the affected server) have no slow down issues.