By using the open source operating system instead of Unix to power its enterprise systems the company saved $17m (£11m) in the third quarter of 2001.
Jacob Levanon, Amazon's director of systems engineering, outlined the achievements and problems with the migration at the Linuxworld conference in San Francisco this week.
The most important saving, he said, came from replacing expensive RISC-based Unix servers with low-cost Intel-based hardware.
"When you migrate to Linux you have incredible flexibility in hardware acquisition," Levanon said. "You have one operating system and many hardware manufacturers that can take advantage of it."
Amazon had been using a collection of Unix systems mainly running on Compaq's Tru64 and Sun's Solaris operating systems. The systems drove the front-end of its e-commerce Web site, its middle-tier infrastructure and its huge backend datacentre.
"Frankly, it worked very, very well for us," Levanon said. However, the company needed a new strategy for new times.
Amazon had to drive down operating expenses as it battled for profitability in a declining Internet economy. At the same time, its operations were growing and the company was beginning to roll out new Web-based services that required more computing power.
"We realised that in that atmosphere we could not sustain our growth over time. We needed to find a much better solution," he said. "Linux made sense to us."
With support from Hewlett-Packard and Red Hat, Amazon began migrating hundreds of servers to Linux. The online retailer gave itself a 120-day deadline for the project that would take it to the start of the holiday shopping season.
By the deadline, Amazon had migrated 92% of its servers from Unix to Linux, leaving only its data centre servers unchanged.
Levanon noted that the move was not without challenges. Amazon develops most of its software in-house and had to move its applications from the 64-bit Unix platform to 32-bit Linux servers.
"Applications that were optimised in 64-bit had to be mapped to a completely new environment, and that was a challenge," Levanon said.
With the majority of its Web and application servers now running Linux, the next major challenge will be the datacentre, said Levanon.
"We are not prepared to stop here," Levanon told Linuxworld delegates. "Our goal is really to do an end-to-end migration to Linux."
However, Linux in the data centre is uncharted territory for Red Hat. The company began shipping its powerful Advanced Server software three months ago and only has a few customers evaluating the use of its software in the data centre, admitted Michael Tiemann, Red Hat's chief technology officer, who joined Levanon during his presentation.
Levanon claimed the deployment of Linux in the datacentre could bring considerable savings to customers.
"Data centre machines are typically some of the most expensive machines, and the cost savings that are presented there are really quite large," Tiemann said.
This was first published in August 2002