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Oracle Tips by Burleson |
Disk I/O Tuning
Chapter 2:
SCSI
Interfaces
Wide Ultra2 SCSI:
Uses a 16-bit bus and supports data rates of 80 Mbps.
As
the SCSI architecture has evolved over the last several years,
especially with the advent of SCSI-3, the definition of SCSI has
become misleading. As with any current standard, SCSI has evolved
over time to:
-
Keep pace with the ever-increasing options available for
computers
-
Keep up with the increasing demands for performance and
stability that are now expected not only of servers, but also
from home PCs and higher-end workstations.
The
most important fact to grasp is that SCSI provides a method for
allowing access to multiple devices on the same "chain" or interface
at the same time. Therefore you should think of SCSI as a bus
technology. The name says it all: Small Computer Systems Interface.
One device on a SCSI bus (say, a computer) can communicate directly
to another (say, a disk drive) without going through the PCI bus,
your system's DMA controller, or anything else aside from the SCSI
controller. One thing to note however is that only one device can
talk to another device at one time over the bus.
The above text is
an excerpt from:
Oracle Disk I/O Tuning
Disk IO Performance & Optimization for Oracle
Databases
ISBN
0-9745993-4-4
by Mike Ault
Oracle Consulting
Services
Burleson
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