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Serial Attached SCSI (SAS) Storage

Serial Attached SCSI - is it worth the wait?
SAS - editor mentions on
A new way of looking at the Enterprise SSD market
DWPD - typical endurance figures in today's enterprise SSDs
the Benefits of Serial Attached SCSI for External Subsystems
Serial Attached SCSI: New Interface, New Storage Rack?
Serial Attached SCSI - Delivering Flexibility to the Data Center
Serial Attached SCSI Timeline - from storage history was the first publication to provide a dedicated Serial Attached SCSI page in November 2001, the same month in which the new standard was first publicly announced.

And for many years this web address you're seeing now - was the home page for SAS news. You can still see archived versions in the internet archive (when it's working).

The first functioning silicon for this was demonstrated in January 2004 by LSI Logic. Host Bus Adapters and chipsets supporting this new standard start shipping to storage system designers in April/May 2004 from various companies.

Here's a timeline of how SAS moved from vaporware to reality.
  • November 2004 - Serial Attached SCSI moved into the top 20 most popular subjects viewed by STORAGEsearch readers for the first time.
  • February 2005 - IBM ships SAS in x366 servers
  • May 2005 - Hitachi Ships 15K RPM SAS Hard Drives
  • June 2005 - HP announces that SAS will be used in ProLiant Dual-Core AMD Opteron-based servers
  • September 2005 - LSI Logic discloses that Dell and Sun will soon ship SAS based servers
  • October 2005 - Seagate & Adaptec Launch 1/2 Price SAS Starter Kit
  • December 2005 - Maxtor & LSI Logic Offer Rebate to Early SAS Adopters
  • January 2006 - StorCase ships first removable SAS drive enclosures.
  • July 2006 - SAS enters the top 10 storage searches by readers for the first time.
  • April 2007 - Hitachi announces 15k RPM, 300GB SAS HDDs.
  • April 2008 - Seagate Technology starts volume shipments of 7,200 RPM SAS compatible terabyte HDDs.
how did SAS play out in the SSD market?

Click here for the SAS SSD timeline - which is updated with real-time news upto 2014

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Serial Attached SCSI readers click here for other storage news
Megabyte mastering serial SCSI
Serial Attached SCSI - how it was positioned at the outset
SAS technology enables SCSI interface solutions beyond Ultra320 to the next-generation Direct Attach Storage enterprise server, storage systems, and high-performance workstation markets while retaining device-level backward compatibility.

The SAS standard defines a device-level enterprise storage interface incorporating SCSI command sets, serial point-to-point interconnections, dual porting, increased addressability and the ability to scale to small form factors. Because the SAS physical layer is compatible with Serial ATA (SATA), users will have the choice of populating their systems with SAS or SATA hard disk drives, or a combination of both.

...from a joint press release by LSI Logic and Tabernus
Editor's notes from storage history

The SAS duplicator ad below appeared on in 2006.
In those days all small form factor SAS disks were hard drives.
7 way Serial SCSI disk duplicator / sanitizer from ICS
Serial Attached SCSI - disk duplicators
from Intelligent Computer Solutions
Why is the new Serial SCSI standard necessary? ('s viewpoint 2001)

Without faster storage - typically upto 50% of the potential performance in modern server processors is wasted.

Serial Attached SCSI (SAS) provides a software compatible upgrade for directly attached SCSI storage which provides much higher performance than Ultra320 SCSI. So this is the least pain next step for SCSI users. Although, as with all new technology there is a learning curve.

The popularity of Internet SCSI (iSCSI) protocol products in the second half of 2003 proved that the base of server owners who are familiar with SCSI - will go a long way to adopt new connectivity options which leverage concepts they trust and are familiar with. Asimilar evolution took place with Ethernet, which started as a 3Mbps standard and still looks viable at 10Gbps. Computer users like stuff that is newer faster and cheaper, but we all know that "newer" also means "buggier" if we are the first users. Anything that reduces the amount of new code and risk along the way gets our vote.

SAS will meet the threat (albeit late in marketing terms) from Serial ATA (SATA), FireWire and USB 2. In fact SAS uses the same electrical interface and cables as SATA. That's good news if you're worried about stocking even more types of cables. It also simplifies the rollout of new test equipment - because products designed for SATA can be adapted to SAS more simply (in theory by firmware upgrades.)

20+ years ago, when SCSI started, it suited the clock speeds and cable transmission driving capabilities of the TTL compatible logic which was the standard at the time. SCSI was also easy to connect using standard low technology ribbon cable. Since then, most of the enhancements in the SCSI standard have focused on getting it to work faster, using higher clock speeds, a wider data bus, lower logic levels and differential signals.

Serial Attached SCSI is the first real attempt in SCSI history to lower cost and simplify the physical connection. Past performance upgrades came from increasing the number of cable cores. But the new high speed serial SCSI cables should be cheaper than the lower performance parallel SCSI ones which they replace. And you won't have to worry any more about those termination nightmares. It's simpler in a serial system to automatically monitor signal quality and dyamically adjust to the cable and connector transmission characteristics.
SSD ad - click for more info

Above - example of an old banner ad from SSD market history which appeared on in the first half of 2013
"rules are made to be broken"
Survivor's Guide to Enterprise SSDs
these were key educational articles introducing SAS
the Benefits of SAS for External Subsystems
This introduction to Serial Attached SCSI (written by Adaptec ) gives you an idea of the performance, compatibilities, applications and roadmap for this new directly attached disk connection standard.

The new SAS products not only provide an upward migration path for parallel SCSI applications but also open the door to a new class of high performance high reliability enterprise systems. the article
Serial Attached SCSI - Delivering Flexibility to the Data Center
by LSI and Maxtor

If you think you already know SAS because you know SATA and traditional SCSI then think again.

Sometimes disruptive technologies wear an unassuming disguise. In fiction, Clark Kent, Frodo Baggins and Buffy Summers at first seem harmless, but we see them change into Superman, the Ring Bearer and the Slayer.

SAS too comes cloaked in plain garb - with a physical layer which looks a lot like SATA. But like the Incredible Hulk there are muscles rippling under that shirt - and you would be wrong to dismiss SAS so lightly. There's a lot more inside this interface than it says on the box as this informative article reveals. the article
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