SAS seizes the spotlight
By Brian Dipert -- EDN, April 29, 2004
With the specifications for second-generation SATA (Serial Advanced Technology Attachment) nearly complete, industry attention is turning to the follow-on enhanced SAS (serial-attached-storage) interface in conjunction with a migration beyond the 3.5-in. hard-disk drive to smaller form factors that reduce power consumption and improve access reliability (see “Speedy simplicity, EDN, Jan 22, 2004, pg 33). At first glance, you might think that, in developing its 15-mm, 2.5-in. Savvio drive family, Seagate simply turbo-charged its 5400-rpm Momentus hard-disk drive (see “Speed searching,” EDN, Oct 30, 2003, pg 101). Seagate demurs at such suggestions, claiming that it’s more accurate to say that the company pared back the specifications of its 15,000-rpm Cheetah drives to come up with Savvio.
Containing 8-Mbyte buffers and with 4.1-msec seek speeds, Savvio drives come in 36.7-and 73.4-Gbyte capacities. Seagate plans to price Savvio units approximately 10% higher than 3.5-in. Cheetah 15K counterparts with equivalent capacities and system interfaces. This pricing might seem strange upon initial inspection, considering that Cheetah 15K not only has a higher rotation speed, but also a lower, 3.7-msec seek latency. Seagate points out, however, that Savvio consumes 40 to 50% lower power, weighs more than 1 lb less, and takes up 70% less volume than an alternative 3.5-in. drive. The low-volume factor enables you to squeeze much higher multidrive storage capacities, along with higher aggregate performance, into a chassis.
Ultra320 SCSI and 2-Gbps FibreChannel Savvio variants are now available in sample quantities, with full production slated for June. Late in the third quarter, 3-Gbps SAS versions will appear; if you’d prefer to have SAS now, call Fujitsu. The company has been shipping samples of its 2.5-in. SAS drives since last fall; for now, they come in a SATA-like single-channel version. (The SAS specification uses the second channel for redundancy, not boosted performance.) Fully featured dual-channel variants are under development. Fujitsu is seemingly sending mixed messages; it also has just unveiled 10,000- and 15,000-rpm, 3.5-in. drives that tout capacities as large as 300 and 147 Gbytes, respectively, and come in both Ultra320 SCSI and 2-Gbps FibreChannel interface variants. However, Fujitsu sees more than 50% of its business migrating within five years to SAS and the 2.5-in. form factor.
Fujitsu Computer Products, 1-408-432-6333, www.fcpa.fujitsu.com.
Seagate, 1-831-438-6550, www.seagate.com.
