Dell is the latest storage supplier to ship external storage enclosures equipped with 2.5-inch SAS drives. And it claims the availability of the compact drives has renewed interest in direct attached storage (DAS) for some applications.
"Introducing a DAS product in this day and time seems unfashionable, but we're finding a DAS resurgence," says Praveen Asthana, director of Dell Enterprise Storage. "SAS is making DAS more scaleable, and we're seeing more applications around DAS. Exchange 2007 can get performance in a DAS without needing a SAN."
Like HP, IBM, Sun, and other suppliers, Dell started replacing older SCSI drives with 2.5-inch SAS drives in its servers over two years ago. While others have been offering JBOD with 2.5-inch drives and Infortrend has shipped external RAID subsystems with them, Dell has hung back, but now claims to be in the "knee of a trend" upward, making it economically feasible to offer 2.5-inch external storage as well.
Dell claims its PowerVault MD1120 takes up 70 percent less space and 50 percent less power than 3.5-inch drives. Each 2U enclosure houses up to 24 drives. Up to 144 drives can fit into 12U of rack space. Up to 21 Tbytes can be handled by one RAID controller (using 144 146-Gbyte drives per enclosure, with up to three enclosures per RAID port).
Dell won't say whose drives it's using, but Fujitsu, Hitachi, and Seagate all offer 2.5-inch SAS drives in capacities of 36 Gbytes, 73 Gbytes, and 146 Gbytes. In addition, Seagate recently unveiled a 300-Gbyte 2.5-inch drive it says will increase a large-scale migration to that form factor for enterprise drives by 2010.