Scsi Is A Key Technology For Storage; Scsi Advantages; Glossary - ATTO Technology UL4D PCI Installation And Operation Manual

1 SCSI is a key technology for storage

Ultra320 SCSI represents the seventh generation of SCSI technology, an I/O interface that increases
performance while maintaining backward compatibility and legacy support.
From its roots in 5 MB/sec. transfer rates, SCSI
has evolved as the leading interface for disk drive
connections in high performance servers. It
features maximum data transfer rates of 320
MB/second, full backward compatibility with
older versions of SCSI protocols and additional
features to improve performance and reliability.
Ultra320 is a powerful storage technology. All
forms of digital content, from e-mail, video, film,
and audio, to streaming video, and imaging, are
Exhibit 1-1 How SCSI has evolved.
Narrow
Data transfer <5 MB/sec
rates
SCSI protocol SCSI-1
Specification SPI-1
Transfer type Single-
Ended

Glossary

Some terms used in the storage industry are defined below. More information is available through the
ATTO Technology website (
Term Definition
ANSI American National Standards Institute
Asynchronous AIP: although most Ultra320traffic is sent synchronously and protected by CRC, some
Information information is still sent asynchronously. AIP implements CRC-level error checking on
Protection asynchronous traffic ensuring end-to-end data integrity.
bit Smallest unit of data a computer can process: a single binary digit with a value of either 0 or 1
byte an ordered set of 8 bits
CRC Cyclic Redundancy Checking, an error-correcting code which calculates a numeric value for
received and transmitted data. If no error has occurred during transmission, the CRC for both
received and transmitted data should be the same.
destination address A value in the frame header of each frame which identifies the port in the node where the
frame is being sent
domain validation Before sending data, domain validation verifies that the physical connection is capable of
handling the negotiated transfer speed. If the system determines that Ultra320speeds are not
feasible, a slower speed is enforced.
1
ATTO Technology Inc. ExpressPCI Host Adapter Installation and Operation Manual
Fast/
Ultra
Narrow
10 MB/sec 20 MB/sec
SCSI-2 SCSI-3
SPI-1 SPI-1
Single- Single-
Ended HVD Ended HVD
) and the SCSI Trade Association (
www.attotech.com
driving the unprecedented growth in storage that
pushes the I/O bandwidth, requiring more
advanced interfaces to handle data transfer.

SCSI advantages

• Backward compatible with older versions of
SCSI. Newer adapters will negotiate to the
lower speeds of legacy devices.
• Minimal investment to upgrade technology.
Older equipment may still be used with newer
equipment. Upgrade does not require
replacement of infrastructure.
Ultra/WIDE Ultra2
40 MB/sec 80 MB/sec
SCSI-3 SCSI-3
SPI-1 SPI-2
Single- LVD
Ended HVD
Ultra160 Ultra320
160 MB/sec 320 MB/sec
SCSI-3 SCSI-3
SPI-3 SPI-4
LVD LVD
).
www.scsita.org