ScaleUp Addresses Many of IIS’ File Uploading Limitations

Posted by Abel Avram on May 05, 2010

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Development,

Architecture & Design

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.NET ,

Performance & Scalability

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IIS 7

LeanServer has created for IIS 7.0 an extension called ScaleUp, solving some of the problems related to file uploading and plaguing Microsoft’s web platform. According to its creators, ScaleUp increases upload speed, supports unlimited upload file sizes, scales up to thousands of uploads per server, and includes progress reporting, streaming and filtering.

ASP and ASP.NET have long had a number of problems uploading files. In the beginning, one could not extract a file from a POST message unless he wrote custom code parsing the post and retrieving the file data. ASP.NET introduced the FileUpload control which improved the uploading process by synchronously loading the POST data into the memory, parsing the data to extract the file, and consequently saving it to the disk. This solution had a number of problems, the most severe one being the quick fragmentation of the memory leading to OutOfMemory exceptions because the entire file would go to memory first before being transferred to disk. ASP.NET 2.0 introduced more enhancements including a disk buffering option which saved to the disk any upload exceeding 80KB. Still, there remained some limitations:

• The maximum size of uploaded files was 2GB (ASP.NET) or 4GB (IIS)
• There was one thread per upload, leading to thread starvation
• Disk buffering had a serious negative performance impact
• Uploads could not be streamed and there was no report on progress

ScaleUp promises to solve all these problems. The features of the framework promise:

• Faster uploads, up to 20x times
• No limit for the upload size
• Scaling up to thousands of simultaneous uploads for server
• Features like progress reporting, streaming and filtering
• Enterprise performance monitoring of the uploading process across servers

Mike Volodarsky, former PM for IIS at Microsoft and currently CTO for LeanServer, has explained how ScaleUp works:

The secret behind ScaleUP is its use of the IIS 7.0’s native extensibility layer to completely replace the platform’s upload handling with its own high-performance preload engine. This allows it to eliminate the pre-existing upload limitations, while allowing any existing IIS-compatible application to handle web uploads with virtually no application changes.

At the heart of ScaleUP’s upload engine is fully asynchronous request preload, which eliminates thread starvation and enables us to fully take advantage of multi-core power provided by today’s servers.

The entire engine is fully asynchronous from reading network data, to parsing multipart/form-data uploads, streaming entity filters, and disk storage. Internally, we use advanced Windows performance technologies like async unbuffered IO, advanced cache management and pretty much every IIS 7.0 trick in the book to significantly boost upload throughput, and reduce resource usage on the server.

Currently ScaleUp is used by MySpace to handle 25 million uploads per day, and they say they reduced the number of uploading servers after installing the IIS extension. ScaleUp can be used for ASP, ASP.NET, and PHP applications and can be used with existing applications without requiring modifications.

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