Slow performance when backing up remote servers with the TCP Offload Engine (TOE) feature enabled on network cards and/or Windows 2003 SP2 Scalable Networking Pack (SNP) is enabled. Please note that most topics discussed in this article are applicable to later versions of Windows Operating System.
Windows 2003 Service Pack 2 introduced a new update called SNP (Scalable Networking Pack) . This utilizes a feature in newer network cards called TCP/IP Offload Engine (TOE ) or TCP Chimney. Some servers that have this feature enabled experience throughput or connectivity issues when used in conjunction with certain NICs (Network Interface Cards) between the media server and remote machines.
- Backup of Local Media Server to B2D (Backup to Disk) runs at a normal throughput rate.
- Backup of Local Media Server to tape runs at a normal throughput rate.
- Backup of Remote Server (One or All) to B2D runs at a normal throughput rate in most instances, but runs slower in some network configurations.
- Backup of Remote server (One or All) to tape is consistently slow or loses connection all together during a backup or restore.
To determine if the TOE Feature is possibly causing the performance issue, disable the feature per the following and run additional remote backups to test:
- Modify the network adapter (NIC) properties to disable Receive Side Scaling or the TOE Option. Contact the Hardware Provider for specific instructions.
- Temporarily disable Windows 2003 SP2 Scalable Networking Pack TCP Chimney Offload feature by issuing the following command at a Windows command prompt (Start, Run, CMD). No reboot is required
- Disable the Windows 2003 SP2 Scalable Networking Pack features (TCP Chimney Offload, Receive Side Scaling , Network Direct Memory Access) by applying the update per Microsoft KB 948496
- Windows 2003 Scalable Networking pack and its possible effects on Exchange - http://msexchangeteam.com/archive/2007/07/18/446400.aspx
- The Microsoft Windows Server 2003 Scalable Networking Pack release - http://support.microsoft.com/kb/912222
- You cannot host TCP connections when Receive Side Scaling is enabled in Windows Server 2003 with Service Pack 2 - http://support.microsoft.com/default.aspx?scid=kb;EN-US;927695
- TCP traffic stops after you enable both receive-side scaling and Internet Connection Sharing in Windows Vista or in Windows Server 2003 with Service Pack 1 - http://support.microsoft.com/default.aspx?scid=kb;EN-US;927168
Netsh int ip show offload
Here are examples of settings from 2 different NIC cards:
Example 1: Output from Netsh int ip show offload:
Example 2 Output from Netsh int ip show offload:
Veritas Support recommends setting all these values to Off / Disabled / None (or whatever value means "off")
- As can be seen above, different NIC manufacturers and drivers may name these attributes differently. Experimentation can be done to identify which settings map to which names by changing the value in the Attribute section of the NIC properties and then rerunning Netsh int ip show offload to see what changed.
- Modifying any of these settings will temporarily disconnect the NIC from the network. Care should be taken when making this adjustment so as not to disrupt any critical activity. Also, consider directly interfacing with the machine rather then using Remote Desktop Control.
- Modifying these settings for most NIC's does not require a reboot to engage the setting. But if this is a great concern, check with your NIC vendor to see if a reboot is necessary, or experiment on a non-production machine before modifying a production machine.
How to observe the Offload State of a TCP connection:
Flow Control Recommendations for NICs: