SCSI to SAS
The storage standard SCSI is set to evolve. According to Gartner, by 2010,
all SCSI drives will move to Serial Attached SCSI (SAS).
Due to the smaller SAS interface, 2.5 inch enterprise-class drives will start
to replace 3.5-inch models. In the long haul, this will mean that data centres
will accommodate more storage without eating up more floor space. Smaller drives
will also reduce power usage, speed data access, and increase the overall capacity
of drive arrays.
At first the changes will be invisible, with new servers coming mid-year with
internal SAS drives instead of the traditional parallel SCSI ones. Although
SCSI technology is changing, enterprises dont have to worry about reworking
their storage infrastructure to prepare for or manage the change. Since the
drives use the same command set as previous SCSI drives, theres no change
needed to the enterprises storage architecture; the SCSI command set and
external interfaces remain unchanged. Also unchanged are the drives head
assemblies and the parts that store and read the data.
Older parallel SCSI drives are incompatible with SAS, so enterprises will have
both sorts of SCSI devices in their DAS and SANs until the older devices are
retired years from now. But that just means maintaining two types of replacement
drives in case of failures, and perhaps rearranging arrays to minimise having
multiple cabinets, some of each type, in the same location.
SAS controllers work with both SAS and SATA drives because the cables are both
physically and electrically the same. This will allow vendors to use the same
power supplies, cases and backplanes in all their products, reducing manufacturing
costs and thus lowering prices to the enterprise.