eBay

　　eBay is a global phenomenon-the world's largest garage sale, online shopping center, car dealer and auction site with 147 million registered users in 30 countries as of March 2005. You can find everything from encyclopedias to olives to snow boots to stereos to airplanes for sale. And if you stumble on it before the eBay overseers do, you might even find a human kidney or a virtual date.

　　eBay Basics

　　eBay is, first and foremost. an online auction site. You can browse through categories like Antiques, Boats, Clothing & Accessories, Computers & Networking,Jewelry & Watches and Video Games. When you see something you like, you click on the auction title and view the details, including pictures, descriptions,payment options and shipping information.

　　If you place a bid on an item,you enter a contractual agreement to buy it if you win the auction. All auctions have minimum starting bids, and some have a reserve price-a secret minimum amount the seller is willing to accept for the item. If the bidding doesn't reach the reserve price, the seller doesn't have to partwith the item. In addition to auctions, you can find tons of fixed-price items on eBay that make shopping there just like shopping at any other online marketplace. You see what you like, you buy it, you pay for it and you wait for it to arrive at your door.

　　You can pay for an item on eBay using a variety of methods, including money order, cashier's check, cash, personal check and electronic payment services like PayPal and BidPay. It's up to each seller to decide which payment methods he'll accept.

　　Just as you can buy almost anything on eBay, you can sell almost anything, too. Using a simple listing process, you can put all of the junk in your basement up for sale to the highest bidder. When you sell an item on eBay,you pay listing fees and turn over a percentage of the final sale price to eBay.

　　Once you register (for free) with eBay, you can access all of your eBay buying and selling activities in asingle location called "My eBay."

　　eBay Infrastructure

　　A series of service disruptions in 1999 caused real problems for eBay's business. Over the course of threedays, overloaded servers intermittently shut down, meaning users couldn't check auctions, place bids or complete transactions during that period. Buyers, sellers and eBay were very unhappy, and a complete restructuring of eBay's technological architecture Followed.

　　In 1999, eBay was one massive database server and a few separate systems running the search function. In 2005, eBay is about 200 database servers and 20 search servers.

　　The architecture is a type of grid computing that allows for both error correction and growth. With the exception of the search function, everything about eBay can actually run on approximately 50 servers-Web servers,application servers and data-storage systems. Each server has between 6 and 12 microprocessors. These50 0r so servers run separately, but they talk to each other,so everybody knows if there is a problem somewhere. eBay can simply add servers to the grid as the need arises.

　　While the majority of the site can run on 50 servers,eBay has four times that.The 200 servers are housed in sets of 50 in four locations,all in the United States. When you're using eBay, you may be talking to anyone of those locations at any time-they all store the same data. If one of the systems crashes. there are three others to pick up the slack.

　　When you're on the eBay Web site and you click on a listing for a Persian rug, your computer talks to Web servers, which talk to application servers, which pull data from storage servers so you can find out what the latest bid price is and how much time is left in the auction. eBay has local partners in many countries who deliver eBay's static data to cut down on download time, and there are monitoring systems in 45 cities around the world that constantly scan for problems in the network.

        （实习编辑：王晓晓）