Product unites powerful PC team

Even though the capacity of PC hard drives is ever expanding, we still often find that we can't put enough data on them, and we certainly can't get the data off of them fast enough.

If the CPU is the speedy hare inside our computers, then the hard drive is the slow tortoise.

At the offices of start-up company Times N Systems Inc., I found a new and unique solution to this problem. The company has invented a way to combine the hard drives on several PCs into one gigantic virtual drive and meld the RAM on these machines into one huge and blindingly fast RAM drive.

At first, the Times N Systems product looked like nothing special. Walking into a lab, I saw an ordinary rack stuffed with several PCs, with one PC at the top. At the back of the rack, I spotted a fiber-optic cable from each of the lower PCs running up to the PC at the top. It was beginning to make sense. The PCs at the bottom contributed their hard drives and RAM, and the PC at the top pulled everything together into one gigantic virtual hard drive and RAM drive.

The only special hardware components are the fiber-optic cables and the unique adapter cards to which they attach. Each PC below the top one runs its own operating system, which can be Linux or Microsoft Corp.'s Windows NT or Windows 2000. The use of off-the-shelf components reduces costs and allows you to add your own PCs to the team.

The team leader PC is called the Shared Memory Node (SMN), and the team member PCs are the Team Processor Nodes (TPNs). Examining the management software on the team leader PC, I saw there are many ways to bring the team member PCs together to make breathtakingly large drives.

As a real-world example, a group of eight PCs with four 36G hard drives on each machine can provide what appears to users as a single 1 terabyte hard drive. Assume that each of these machines has a modest 512M left over after the operating system and other requirements are subtracted, and the resulting virtual RAM drive is 4G.

This is far from the limits for Times N Systems. If you place 4G of RAM in each PC and use 16 PCs, then allowing for software overhead, you can construct a RAM drive that's 60G in size. For perspective, this is substantially larger than the largest solid-state disk available on the market.

I was delighted to find that these virtual drives appear to the user to be no different than any other drive except for their unusual size and speed. And the speed of hard drive access will not decrease as you add additional PCs to the system.

Examining the management software in detail, I was surprised at the variety of options for configuring the virtual drives. The feature I liked best is something new called chained declustering. This feature is like Level 5 of Redundant Array of Independent Disks, only better. Like RAID 5, it spreads data over several drives, making the system faster because it allows parts of large files to be accessed simultaneously from different drives. But where RAID 5 allows the system to survive the loss of a hard drive, chained declustering allows it to survive the loss of an entire PC.

I do recommend using the feature to mirror RAM drives to hard drives. This will not affect speed of reading the RAM drive, but writing to the hard drives will be slower than writing to the RAM drive.

Times N Systems sells its product either as a complete system, including all the PCs, or as a bundle to add to your existing servers. I recommend — but it's not strictly necessary — using hard drives that are all of the same size for ease in configuring the virtual hard drives.

The Times N Systems product could easily handle the huge amounts of data generated by, for example, the space program and the weather bureaus. In call centers, it can provide faster response and greater call completion. The product also will enable Web sites to handle more transactions faster, while retaining the original servers.

Earl Greer is a senior network analyst at a large Texas state agency. His Internet address is Earl.Greer@dhs.state.tx.us.