Following Up a Question About the Server Service

I have a few questions regarding "Resolving Server Service Errors on a SAN Disk-Array Connection," April 2003,, InstantDoc ID 37882, in which a reader writes about a problem booting a Windows 2000 server from QLogic's SANblade 2200 to XIOtech's MAGNITUDE disk array. To prevent the Server service from crashing during heavy loads, you advise the reader to use a switch to connect the Storage Area Network (SAN) components; you also recommend a registry modification that might solve the problem. Why is using a switch preferable? And is modifying the registry the only way to fix the problem?

As I state in the article you mention, the underlying problem (in my opinion) lies with Win2K's system for disk I/O queuing rather than with the MAGNITUDE. That said, the MAGNITUDE has the unique ability to handle multiple disk I/Os from different sources simultaneously when those I/Os come through a switch. When using a switch, the MAGNITUDE'S queue depth and performance increase according to the number of servers connecting to the array through one port. When only one server (even a powerful one) gives the array all the work, however, the single thread can create a bottleneck.

Some people might be reluctant to modify the registry on the Win2K machine to specify the maximum number of receive and raw receive buffers that the system can allocate and the number of free connection blocks that the system maintains for each endpoint. Instead of editing the registry, you can try several other approaches.

First, make sure that a problem with the Win2K system's NIC isn't the culprit. Microsoft claims that it's seen reports of event-log errors 2021 and 2022 on machines that use an outdated NIC driver or one that isn't recommended for the array in use.

Second, make sure that your disk array is functioning properly. If you use the Win2K server as an application server as well as a file server, you might be overtaxing your array or local disks.

Third, try optimizing the Win2K server's network settings. To do so, open the My Network Places Properties dialog box, then open either the Active Network Connection object's or the Local Area Connection object's Properties dialog box. Select and highlight the File and Printer Sharing for Microsoft Networks check box, then click Properties. If you use the server as a file server only, choose the Maximize data throughput for file sharing option on the File and Printer Sharing for Microsoft Networks Properties dialog box. If you use the server as both an application server and a file server, however, be aware that this option might degrade the server's performance as an application server.

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