HP is set to ship its ProLiant servers with smaller, 2.5-inch (6.35 cm) hard drives based on the Serial Attached SCSI (SAS) hardware interface. The company said that this would allow it to cram more drives into each machine.

The manufacturer has been working with storage vendors such as Seagate Technology and Fujitsu . for several years to develop the smaller drives for its servers, which presently ship with 3.5-inch drives.

"This is the beginning of a transition," said Paul Perez, vice president of storage network and infrastructure with HP's ProLiant division. "What we want to do is offer the option of small form-factor SAS drives across our product line starting in May."

At that time, HP expects to support the standard with its ProLiant 380 and 360 rack-mounted servers, as well as its ProLiant 350 and 370 tower-style servers, according to Perez. SAS will replace SCSI as the default interface for all ProLiant servers by 2006, he said.

HP also plans to support SAS in its StorageWorks, BladeSystem, and Integrity products, he said.

Because the SAS drives are smaller than the 3.5-inch SCSI drives HP currently sells, the company will be able to pack a larger number of hard drives into each machine. "You will see an increase in the number of drives of anywhere between a third and 50 percent," Perez said.

Perhaps more important for customers is the fact that SAS is compatible with a competing hardware interface, Serial ATA (Advanced Technology Attachment). That means customers will have the option of purchasing less expensive Serial ATA drives with their systems, said David Freund, an analyst with Illuminata.

HP said that customers would be able to mix both SAS and Serial ATA drives in the new systems.