Why doesn't HttpPostedFile perform as advertised and buffer downloads to disk rather than memory?

I am uploading large files to an ASP.NET server using a standard HTML `<input>` control posting multipart-form data. This is an ASP.NET MVC application. According to MSDN, the `HttpPostedFile` class buffers to disk out of the box: "Files are uploaded in MIME multipart/form-data format. By default, all requests, including form fields and uploaded files, larger than 256 KB are buffered to disk, rather than held in server memory." I assume this means that when I access `HttpPostedFileBase` in my controller, that when I access the `HttpPostedFileBase`'s `InputStream` property, I can write the file buffer somewhere without having to worry about the server running out of memory, which is obviously an unworkable solution. Here's a bit of pseudocode for how I'm handling each of the incoming files from `HttpPostedFileBase`. ``` for(var i = 0; i< Request.Files.Count;i++) { var fileBase = Request.Files[i]; if (fileBase.ContentLength == 0) { continue; } // One thread per file ThreadPool.QueueUserWorkItem(state => { // Read from fileBase.InputStream }, null); } ``` My web.config's httpRuntime block looks like this: ``` <httpRuntime executionTimeout="1200" requestLengthDiskThreshold="2097151" maxRequestLength="2097151" useFullyQualifiedRedirectUrl="false" minFreeThreads="8" minLocalRequestFreeThreads="4" appRequestQueueLimit="100" /> ``` My implementation works, multiple files are uploaded as expected, except that the same amount of memory required to buffer the entire payload is consumed by the server. I have to assume that the InputStream is buffering everything. When I upload more files than I have memory, it predictably crashes with an `OutOfMemoryException`. Here's an image of the memory spike when uploading an 800mb file. I know I could use a Flash/Silverlight widget or write a custom `HttpModule` to intercept uploads and handle them myself, but the current requirement would work flawlessly if `HttpPostedFile` did what MSDN says it does (or I'm doing it wrong).