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POTuning a WCF File Server
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copied!<p>I'm tuning a server and need some guidance. This server provides the following features:</p> <ol> <li>an ASPX page with a DB call that is downloaded approximately every 3 minutes by several thousand machines</li> <li>a simple ASP.NET admin web site used by a tiny number of people but that must be highly available</li> <li>a WCF service that provides file synchronization to another several thousand clients using BasicHttpBinding and Streamed messages.</li> </ol> <p>When an update is available to the file-sync clients (#3), they swarm the server clamoring for their new data. Without aggressive throttling they eat up all available ASP.NET worker threads and cause #1 and #2 to hang. This, as the kids say, sux0rs.</p> <p>I've reproduced this problem on a 4-proc server. With a test client creating 100 simultaneous downloads, I see that 48 downloads are running simultaneously; in perfmon I see the remainder queueing up in ASP.NET->Requests In Application Queue. This jibes with the "12 concurrent threads per CPU" default setting described <a href="http://msdn.microsoft.com/en-us/library/ms998549.aspx#scalenetchapt06_topic8" rel="nofollow noreferrer">in this article</a>. CPU and memory look fine; it's really just shuttling bytes with no processing.</p> <p>As I see it, there are a couple of things I could do, possibly in concert.</p> <ol> <li>Up the maxIOThreads and maxWorkerThreads in machine.config</li> <li>Set up a web garden</li> <li>Redo the client so downloads are handled directly instead of via WCF (eg link directly to the file instead of streaming it in a message).</li> </ol> <p>My questions:</p> <ul> <li>Aside from trial and error, what are good guidelines for increasing the number of threads given that each is going to be in use for a pretty long time with low CPU/memory usage? If I go this route, how do I ensure the task switching for the increased number of threads doesn't overwhelm the system and cause more problems?</li> <li>Would a web garden help in this situation?</li> <li>Will I see much better performance if I get the download out of WCF and let IIS handle it entirely?</li> </ul> <p>Best, roufamatic</p>

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