And the Sign of the Beast is 6 (Gbps that is)

“The two primary interface standards for storage devices are
SATA (Serial Advanced Technology Attachment) and SAS (Serial
Attached SCSI). Both have been around for a number of years, SATA
first appearing in 2003 and SAS appearing in 2004. Also, both of
them have similar throughput performance currently at 3 Gbps (SATA
started at 1.5 Gbps while SAS started at 3.0 Gbps). However, lately
both protocols had been showing their age, particularly with the
advent of SSD (Solid State Drives). However, the committees that
oversee the protocols have not been idle and have created the next
generation for each protocol – 6 Gbps.

“Who needs 6 Gbps?

“Hard drives are increasing in throughput performance but at a
rather slow rate meaning that the performance of a single hard
drive hasn’t changed all that much in recent years. While
perhaps not the best source of benchmarks and testing, Toms
Hardware did run a very interesting article that examined desktop
hard drives from the last 15 years. It is a very nice retrospective
of how hard drives have changed ending in 2006. In particular, this
chart shows that the performance of a single SATA drive in 2006 was
about 64 MB/s. The performance of single hard drives today are
about the same. So if individual drive performance is somewhat
stagnant, why do we need a faster storage interface? The answer is
fairly simple – either we have multiple drives attached to a single
interface (i.e. RAID) or we are using SSD’s (Solid-State
Drives) or a combination.

“The stated throughput of either a current SAS or SATA
controller is 3 Gbps. A 3 Gbps interface has a theoretical
throughput of 375 MB/s (Mega-Bytes per second) but actual
throughput is a bit lower than that. Internal to the storage system
there is data and handshaking processes taking place that reduce
throughput. Also, the data is transmitted in packets (sort of like
a network) that can also reduce throughput. The ASIC on the
controller as well as the details of the drive performance itself
can also affect performance. A rule of thumb for the 3 Gbps
interface is that the maximum throughput is about 275-300
MB/s.”

Complete
Story