Course 2: SCSI School
SCSI Types & Specifications
As interface technologies have advanced, many of the key selling points of the
original SCSI have been replaced by the newer, faster interface properties of
more modern standards such as SATA/SATA II etc. It is important to note that
while many organizations have replaced SCSI with its successors, many
organizations still prefer the benefits offered by legacy SCSI devices.
As such, SCSI is far from obsolete.
It is also of interest to note that SCSI is still evolving. Newer standards,
such as SAS (Serial Attached SCSI) and iSCSI continue to flourish, even when
compared to the newer standards. iSCSI, for instance, has achieved broad
support from operating systems such as Windows, Linux and Netware to name
a few, while Serial Attached SCSI continues to grow in enterprise settings
based on the impressive data transfer rates it has to offer.
iSCSI
Also called “Internet SCSI”, ISCSI was developed by the IETF (Internet
Engineering Task Force), and became an official standard in February of 2003.
This IP-based standard is used to transfer data by carrying SCSI commands
over IP networks, and link data storage devices via an IP-based network.
iSCSI supports a Gigabit Ethernet interface, and allows systems capable of
supporting the iSCSI interface to directly connect to standard Gigabit
Ethernet switches and/or IP routers. Of particular importance to SAN
(Storage Area Network) technology, iSCSI enables a SAN to be deployed
within a LAN (Local Area Network), WAN (Wide Area Network) or MAN
(Metropolitan Area Network).
SAS
Another recent offshoot of the SCSI standard, SAS (Serial-Attached-SCSI)
offers users a replacement for the parallel SCSI interface. Used primarily
for the transfer of data to and from devices such as hard drives, optical
drives etc, SAS is a serial communication protocol for direct attached
storage devices.
Designed for the corporate and enterprise markets, SAS offers users
much faster data transfer rates (up to 3Gbps) than were previously
available. Another key feature of Serial-Attached-SCSI is that it
offers backwards-compatibility with the SATA interface. Although
SAS is a Serial communication, unlike traditional SCSI devices, it
still uses SCSI commands with SAS End devices.
Next – Chapter 8 - SCSI Products
|
|
|
|
