If they develop it, will it work? Exploring Gmail

Google Inc.'s free e-mail service, Gmail, has received a huge amount of interest in the past week thanks mostly to its claim that it will offer 1GB of storage to each user.

It seems safe to assume that within a few days of the service going live, it will have several million people apply for an account. One gigabyte multiplied by several million could represent the world's largest-ever storage order. It could also represent the world's single largest privacy problem due to Google's business model where content-related ads will pop up as you read your incoming mail.

Microsoft Corp.'s Hotmail and Yahoo Inc. offer just a few megabytes of free e-mail storage each. Users pay for additional storage. Google is comprehensively disrupting this model of Web-hosted e-mail. And already a Mac web-hosting service, Spymac Network Inc., is also offering a free gigabyte e-mail storage to its members.

If one million users, say, take Gmail up then, on the face of it, 1PB, one petabyte -- that's one million gigabytes, of hard disk would be needed. Double that for redundancy, add in more for indexing, and some lucky supplier could find a 2.5PB HDD order in the in-tray.

But Google doesn't work like this.

As we described, Google operates a massively distributed server and storage design using clustered Linux X86 server nodes with one or two hard drives each. The servers store Google's web page index separately from the web documents themselves.

A Google spokeswoman confirmed: "Gmail is built on existing Google search technology, letting people quickly search over the large amount of information in their emails. Using keywords or the advanced search feature, Gmail users can find what they need, when they need it." The Gmail service, incidentally, is already up and running and all Google employees have their own "gmail.com" address.

But such a system architecture is unusual in a world where storage networking is the norm. It may also be a gamble for the search engine giant, with storage experts telling us that alternative methods are better when dealing with so much data.

Google's system can be defined as direct-attached storage (DAS), where, oddly enough, storage is attached directly to a computer. The vast majority of big storage networks in use are network-attached (NAS) -- where a data server on a network provides storage accessed via the network -- or storage area network (SAN) -- a high-speed subnetwork of shared storage devices.

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