CacheFlow revs up server-side Web cache

Ever-increasing Internet activity and the demand for quicker, richer Web content has put serious strain on corporate and e-commerce Web servers alike. CacheFlow's new Server Accelerator 725, which off-loads content-delivery tasks from Web servers, can significantly boost Web server performance - by eight-fold in our recent tests.

The SA 725 is a Web-caching appliance designed to sit in front of a Web server or server farm. It uses proprietary algorithms that eliminate the need to serially process setup and get requests for each object requested from a Web page.

The SA 725 runs on the company's proprietary, embedded operating system, CacheOS, and improves Web page response times by caching frequently requested content and off-loading Secure Sockets Layer processing from the Web server through a built-in SSL Accelerator. Off-loading SSL encryption from the Web server results in substantial increases in Web server performance.

Using CacheFlow's SA 725 on our test network, we reduced Web server CPU utilization from 90.6% to zero, increased transactions per second from 13.34 to 105.10 and decreased response times from 0.37085 seconds to 0.04654 seconds.

In addition to delivering significant performance boosts, the SA 725 was easy to install and offered excellent redundancy. However, incomplete documentation and a problem uploading server logs to an FTP server mar an otherwise straightforward management application.

Web pages comprise many different objects such as logos, script and text, which are retrieved serially when a user requests a certain page. For each object, a TCP session setup followed by an HTTP get request takes place between the user's browser and the Web server. Because there are multiple objects per page, there are multiple setup and get requests, which causes delays for end users.

The SA 725 eliminates delays through a proprietary algorithm called Pipeline, which lets many TCP connections occur simultaneously. These objects are sent directly from the SA 725 to end users as fast as a browser can request them.

CacheFlow uses another proprietary algorithm, the Adaptive Refresh Algorithm (ARA), to determine which objects on the Web page are most frequently requested. The ARA develops usage models based on how often an object is changed on the Web server and determines a refresh pattern for each object. The SA 725 automatically performs freshness checks with the Web server to ensure old content is replaced. The ARA determines which objects will take the most time to process and assigns items with longer response times a higher priority.

This combination of parallel processing of setup and get requests, object refreshment and priority assignment, as well as the off-loading of SSL processing, combine to produce a substantial performance boost.

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