It would be a stretch to say that Western Digital's announcement of their S25 line of SAS drives was a surprise. Ever since they released the VelociRaptor early last year, I've been waiting for someone over there to slap an SAS interface on the little sucker. Now that they have, and a 600MB/s one to boot, I got Tom McDorman, who runs WD's enterprise storage group, on the phone to explain how SAS drives from WD fit in the datacenter market. The conversation changed my views on the drive market and the evolution of storage in the datacenter.
First, let me say I love how WD can use hard mechanical engineering involved in building a highly reliable 10K RPM 2.5" HDA to deliver their whole performance line. Seagate, Hitachi and Tojitsu (Fujitsu's drive division now owned by Toshiba) have been sticking different electronics on the same HDA for years to deliver SCSI, FC and SAS versions, but WD takes it one step further, mounting the 2.5" drive in an aluminum casting so it can be used in servers and RAID systems designed for 3.5" drives.
The casting, in addition to providing the obvious mechanical connections to mount the drive in a 3.5" space, is also thermally linked to the HDA and acts as a huge heat sink while providing channels for multi-directional airflow. As a result, a VelociRaptor in a 3.5" bay runs about six degrees Celsius cooler than it would in the cheap plastic adapters I used to mount an Intel SSD in my desktop.
On the other hand I went on record a few weeks ago, saying that the days of the 10K RPM drive were numbered. Well, it looks like I was wrong. According to McDorman, 15K RPM drive sales are down while sales of I/O oriented drives in total are roughly flat. Seems that a few SSDs are replacing many short stroked 15K RPM drives in enterprises with very high I/O requirements and 10K RPM drives are making up the middle tier.
Western Digital believes the enterprise market will be about 50:50 10K RPM and capacity oriented drives in a few years. As a result they denied the rumors floating around last year, which I never believed in the first place, that they were working on 20K RPM drives.