Serial attached SCSI is leading the pack of storage interfaces - Storage Networking

Computer Technology Review, Feb, 2003

From the SATA perspective, the advantages of using a Serial Attached SCSI platform are clear:

* Compatible connections allow common cabinetry for desktop and enterprise applications.

* Addressability up to 1024 ports.

* Built in upgrade path from SATA drives to Serial Attached SCSI drives and enterprise applications.

FC and Serial Attached SCSI

Both FC and Serial Attached SCSI offer the maturity, richness, depth and scope of the SCSI command set. They are differentiated by their drive-to-drive connectivity, their inter-box connectivity and their addressability. FC's combination of shared media access, data rate, optical support and fabric compatibility has made it the interface of choice for SANs and high-speed switching environments. Serial Attached SCSI systems are not yet on the market, but they will be built on the strong foundation laid by the SCSI protocol and the serial technology of FC.

For the first time since the market has been segmented into desktop and enterprise applications, Serial Attached SCSI provides a direct link between them and provides the continuity required to make all three interfaces complementary storage solutions.

The SCSI Trade Association is based in San Francisco, CA.

DRIVE COMPARISON TABLE

                                    SATA


PERFORMANCE (Access to Data)
Latency   Seek Time                 13msec @ 7200rpm
Command Queuing and Reordering      LBA based
Rotational Vibration                5 rads/sec/sec
Typical I/Os per sec/drive (no RV)  77
Typ I/Os per sec/drive              35
 (10 rad/sec (2))
Typ I/Os per sec/drive              < 7
 (20 rad/sec (2))
Duplex Operation                    Half

CUSTOMIZATION
Unique Code and Hardware            Limited
Variable Sector Sizes               No
Mode Page Parameter Control         No
Inquiry Data                        No
Diagnostic Pages                    No
Capacity Controls                   No

INDICATORS
Activity LED                        No
Fault LED                           No

RELIABILITY
MTBF                                600K Hrs
Duty Cycle                          8 X 5
Interactive Error Management        No
Internal Data Integrity Checks      No
Dual Port                           No

                                    Serial Attached SCSI
                                    or Fibre Channel

PERFORMANCE (Access to Data)
Latency   Seek Time                 5.7msec @ 15K rpm
Command Queuing and Reordering      LBA (1) and RPS (2) based
Rotational Vibration                21 rads/sec/sec
Typical I/Os per sec/drive (no RV)  319 (3)
Typ I/Os per sec/drive              319 (3)
 (10 rad/sec (2))
Typ I/Os per sec/drive              310 (3)
 (20 rad/sec (2))
Duplex Operation                    Full

CUSTOMIZATION
Unique Code and Hardware            Extensive
Variable Sector Sizes               Yes
Mode Page Parameter Control         Yes
Inquiry Data                        Yes
Diagnostic Pages                    Yes
Capacity Controls                   Yes

INDICATORS
Activity LED                        Yes
Fault LED                           Yes

RELIABILITY
MTBF                                1.2M Hrs
Duty Cycle                          24 X 7
Interactive Error Management        Yes
Internal Data Integrity Checks      IOEDC (4)
Dual Port                           Yes

(1)Logical Block Address

(2)Rotational Position Sensing

(3)Queue = 16

(4)Input Output Error Detection Code