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Chapter 8 All About SCSI.

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Presentation on theme: "Chapter 8 All About SCSI."— Presentation transcript:

1 Chapter 8 All About SCSI

2 You Will Learn… About basics of SCSI (Small Computer System Interface) technology and components How SCSI hard drives compare to IDE drives How to install a SCSI device Some troubleshooting tips for SCSI

3 SCSI Basics Standard for communication between subsystem of peripheral devices and system bus Bus can contain/be used by up to 7 or 15 devices, depending on SCSI standard Bus controller can be either: An expansion card (host adapter) Embedded on motherboard Faster, more expensive, more difficult to install than similar IDE devices

4 The SCSI Subsystem Host adapter Device drivers
Card inserted onto expansion slot on mother board Manages all devices on SCSI bus Supports internal and external SCSI devices Forms a single daisy chain with devices Device drivers Enable OS to communicate with a host adapter

5 The SCSI Subsystem Every SCSI bus subsystem requires a SCSI controller and unique SCSI IDs assigned to each device, including the host adapter

6 The SCSI Subsystem

7 IDE vs. SCSI Bus Communication

8 Issues to Consider when Selecting a Host Adapter
BIOS Expansion slot Bus mastering

9 Vendors for SCSI Host Adapters

10 SCSI Device Drivers Enable OS to communicate with a host adapter
Two popular driver types ASPI (Advanced SCSI Programming Interface) – more popular of the two CAM (Common Access Method)

11 Variations in SCSI Bus width Signaling methods used on SCSI cables
Connectors used with SCSI cables Termination SCSI-1, SCSI-2, and SCSI-3

12 Bus Width Narrow SCSI (8 bits) Wide SCSI (16 bits)

13 Signaling Methods Used on SCSI Cables
Single-ended (SE) Send a signal on pair of twisted wires; one carries voltage, the other is a ground Differential Send a signal on pair of twisted wires; both carry voltage, and the signal is calculated to be the difference between the two voltages High Voltage Differential (HVD) Low Voltage Differential (LVD)

14 Signaling Methods on SCSI Cables

15 SCSI Cables

16 Signaling Methods on SCSI Cables

17 Connectors for SCSI Cables

18 Connectors for SCSI Cables

19 Termination Prevents echo effect from electrical noise and reflected data at end of SCSI daisy chain Single-ended SCSI cables use: Passive terminators Active terminators Forced perfect terminators (FPTs) Differential cables use either HVD or LVD terminators

20 Termination

21 SCSI-1, SCSI-2, and SCSI-3 SCSI-1 = Regular SCSI SCSI-2 = Fast SCSI
8-bit data bus 7 possible devices SCSI-2 = Fast SCSI Common command set 16-bit data bus 15 possible devices Mandatory parity checking SCSI-3 = Ultra SCSI Supports both parallel and serial data transmission Supports FireWire connections Data transfer of 320 MB/sec

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24 Comparing IDE and SCSI IDE supports only four internal devices; SCSI supports both internal and external and allows you to add more SCSI devices are generally of higher quality than IDE devices and more expensive IDE devices require separate IRQ for each device; SCSI requires only one for entire chain continued…

25 Comparing IDE and SCSI Both are generally backward-compatible
SCSI hard drive with supporting host adapter and cable costs more than an IDE hard drive SCSI subsystem provides faster data transfer than an IDE drive SCSI generally provides better performance than IDE; often used on high-demand servers continued…

26 Comparing IDE and SCSI Good host SCSI host adapter allows connection of other SCSI devices to it With SCSI, two or more devices can operate simultaneously; with IDE, only one IDE drive on an IDE channel can be busy at a time

27 SCSI Installation Set jumpers or switches on host adapter and install it on motherboard Assign SCSI ID with jumpers or switches Attach cabling to host adapter and each device Verify termination at both ends of daisy chain Power up one device at a time Install drivers and software

28 Installing a Host Adapter Card with Windows 9x/2000/XP
Install card in expansion slot Change/verify default settings using setup program Verify settings under Advanced Configuration Options Windows supports host adapter; it loads device drivers automatically and installs host adapter Use Device Manager to verify correct installation of host adapter Install external SCSI device

29 Installing a Host Adapter Card with Windows 9x/2000/XP

30 Installing a Host Adapter Card with Windows 9x/2000/XP

31 Setting Device IDs During Installation
With SCAM-compliance, SCSI IDs are assigned automatically Without SCAM compliance, set device SCSI IDs manually Each ID must be unique; no two devices on same SCSI channel can have same ID number For narrow SCSI, use IDs 0-7 For wide SCSI, use IDs 0-15 Host adapter usually has ID 7

32 Setting Device IDs During Installation
To set IDs for external devices, use either push-button selector or rotary selector To set IDs for internal device, use set of jumpers on the device

33 Setting External Device IDs

34 Setting Internal Device IDs

35 Installing a SCSI Hard Drive
Make sure host adapter and cables are compatible with SCSI drive Configure SCSI host adapter and SCSI hard drive so they can communicate with each other as follows: Set SCSI IDs Disable/enable disk drive and hard drive controllers Check terminating resistors Run CMOS setup for a SCSI system Load SCSI device drivers

36 Troubleshooting SCSI Devices
General tips Installation problems Booting problems

37 General Troubleshooting Tips
Keep notes and read documentation Add one SCSI device at a time Use good quality components Limit cable length

38 Problems Installing SCSI Devices
Turn on external devices first, then computer Check connections Verify correct termination (common cause of problems) Verify most updated BIOS Install PCI host adapter in PCI bus that supports bus mastering

39 Booting Problems Confirm BIOS setup drive configuration is set to “No Drives Installed” Verify that SCSI drive is partitioned, has a primary partition, and boot partition is set as active Back up SCSI hard drive and do low-level format on it

40 Chapter Summary How SCSI technology works to provide better performance and greater expansion capabilities for many internal and external devices Advantages and disadvantages of SCSI


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