Transfer speeds and capacities for 3.5-inch hard disk drives continue to ratchet upwards, even as advancements in 2.5-inch systems and even flash technology threaten to supplant them in the enterprise.

Seagate Technology this week set new benchmarks for its product line with the Cheetah drive, a 15k model that can hold up to 450 GB and offers a sustained transfer rate of 147 MBps -- nearly a one-third improvement over existing models -- using either iSCSI or Fibre Channel interfaces. Despite the increased performance, the system has a lower idle speed that reduces power consumption some 60 percent.

Expect the new drive to show up in upcoming StorageWorks arrays from HP, as well as the new SuperServers from Super Micro Computers. However, the Cheetah's position as top dog in the 15k 3.5-inch space may not last long, as Fujitsu is said to be working on a 600GB drive.

All of this begs the question, what is the best drive for enterprise environments undergoing the dramatic changes wrought by virtualization, consolidation and high-speed networking? The 3.5-inch drive is still considered by many to be the workhorse of the enterprise, but much of the industry is, in fact, migrating to the 2.5-inch form factor, and many vendors are actively pushing solid-state drives for the enterprise.

When it comes to comparing one drive against another, one of the key specifications is rotational speed. Those that spin on the order of 15,000 rpms, like the Cheetah drive, are aimed mainly at primary storage from which data is retrieved quickly and often. Slower drives, such as Samsung's new three-platter F1 device, can push capacity to 1 TB, although the 7200 rpm speed makes it more suitable for nearline or secondary storage.

There is also the ever-present specter of drive failure to worry about. While most new models offer MTBF ratings of a million hours or more, it takes an expensive RAID system to ensure that data lost to a bad disk isn't gone for good. But a British company called Retrodata says it has a fix for the problem in the form of the System P. EX platter extraction system. The company claims its system allows storage operators to pull platters from a 3.5-inch drive, even those with shock-absorption technology, without specialized training.

The sad fact is that drive technology is likely to become even more varied as new technologies like perpendicular recording make their way out of the lab. But even as the technology evolves, the old benchmarks of speed, capacity and reliability will still apply.