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Types of System Buses
Types of Disk Subsystems/Protocols - Quick Reference
Table of Content
IDE / ATA
EIDE / ATA2
Ultra ATA / Ultra DMA
SCSI (Small Computer Systems Interface)
Serial Storage Architecture (SSA)
Fibre Channel
Serial ATA
Storage Area Network (SAN) / Network Attached Storage (NAS)
IDE / ATA
Electronic controller card built into the hard drive itself
Two channels with a maximum of two disk drives per channel (one designated as Master and the other as Slave)
Uses 40-pin cable
LImited to 18 inches in cable length, using parallel data transfer
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EIDE / ATA2
Same general layout of IDE, but can achieve faster data transfer rates due to increases in technology
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Ultra ATA / Ultra DMA
Improves performance by using Direct Memory Access (DMA) to allow the drive to access main memory without involving the processor
Connector heads for Ultra ATA cables are typically in blue to distinguish it from a IDE/EIDE cable
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SCSI (Small Computer Systems Interface)
Pronounced "skuzzy"
More flexible and efficient
More devices can be connected; externally or internally
SCSI devices needing to transfer data between itself can be handled by SCSI controller, the CPU need not be involved
Uses a host adapter to improve performance and allow more devices to connect both internally and externally
Both ends of the SCSI chain must be terminated
Three main standards
SCSI-1 (aka Narrow SCSI)
Adopted in 1984
8-bit wide bus
5Mbps transfer rate
7 devices can be attached to the same cable
6 meter maximum cable length
SCSI-2
Adopted in 1994
8- (Fast SCSI -2) and 16-bit (Wide SCSI-2) bus
20Mbps transfer rate
15 devices can be attached to the same cable
25 meter maximum cable length
SCSI-3 (aka Ultra SCSI)
Adopted in 1998
16-bit wide bus
300+Mbps transfer rate
15 devices can be attached to the same cable
25 meter maximum cable length
Ultra3 Wide SCSI
16-bit wide bus
80 MB/s
15 devices can be attached to the same cable
25 meter maximum cable length
Ultra3 SCSI (aka, Ultra-160, Fast-80 Wide)
16-bit wide bus
160 MB/s
15 devices can be attached to the same cable
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Serial Storage Architecture (SSA)
Invented in 1990 by IBM
Can support 192 hot swappable drives
Supports full-duplex communication at over 40Mbps per channel
Replaced by Fibre Channel
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Fibre Channel
Introduced in 1988
Allows hundreds of devices to be connected through a loop
Original version had data transfer rate of 12.5 Mbps
128GFC "Gen6" introduced in 2016 offers data transfer rate of 12.8 Gbps
Active development expected to continue through 2022
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Serial ATA
Uses 4 wires to carry a serial (one bit at a time) signal through the cable. This allow for more flexibility and longer cables as well as faster data transfer
Data cable is 7-pin
Generations:
SATA/150 (aka SATA1) - first generation, 1.5 Gb/s
SATA/300 - 3.0 Gb/s
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Storage Area Network (SAN) / Network Attached Storage (NAS)
Use the network and even the Internet to access data that is stored for the client in large "server farms"
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