1 / 27

Understanding SCSI: Basics, Components, and Performance Comparisons

This chapter delves into SCSI (Small Computer System Interface), an important standard for communication between peripheral devices and the system bus. It covers how SCSI can connect up to 15 devices, speed comparisons with IDE devices, and the necessity of a SCSI controller. Key components like host adapters, device drivers, and variations in SCSI—such as SCSI-1, SCSI-2, and SCSI-3—are discussed. It also explains termination methods, the importance of unique SCSI IDs, and the differences between SCSI and IDE in performance and application in corporate environments.

hana
Télécharger la présentation

Understanding SCSI: Basics, Components, and Performance Comparisons

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter 22 All About SCSI

  2. 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 • Bus requires controller embedded on motherboard or host adapter inserted into an expansion slot • Faster, more expensive, more difficult to install than similar IDE devices • Mostly used in corporate settings A+ Guide to Managing and Maintaining Your PC, Fifth Edition

  3. The SCSI Subsystem • Enables two devices on SCSI bus to pass data between them without going through CPU • Requires SCSI controller and unique SCSI IDs assigned to each device, including host adapter • Components • Host adapters • Device drivers A+ Guide to Managing and Maintaining Your PC, Fifth Edition

  4. SCSI Host Adapter A+ Guide to Managing and Maintaining Your PC, Fifth Edition

  5. IDE versus SCSI Bus Communication A+ Guide to Managing and Maintaining Your PC, Fifth Edition

  6. Host Adapters • Manage all devices on SCSI bus • Support internal and external SCSI devices • Form a single daisy chain with devices A+ Guide to Managing and Maintaining Your PC, Fifth Edition

  7. Bus Mastering • Bus master attached to PCI bus can access memory and other devices without accessing the CPU • SCSI host adapter does not require a DMA channel A+ Guide to Managing and Maintaining Your PC, Fifth Edition

  8. SCAM-Compliant • Can assign SCSI IDs dynamically at startup • Two levels • Level 1 requires that the devices – but not the host adapter – be assigned an ID at startup by software • Level 2 requires that the host adapter – as well as the devices – be assigned an ID at startup by software A+ Guide to Managing and Maintaining Your PC, Fifth Edition

  9. SCSI Device Drivers • Enable OS to communicate with a host adapter • Two popular types • ASPI (Advanced SCSI Programming Interface) – more popular of the two • CAM (Common Access Method) A+ Guide to Managing and Maintaining Your PC, Fifth Edition

  10. Variations in SCSI • Bus width • Signaling methods used on SCSI cables • Connectors used with SCSI cables • Termination • SCSI-1, SCSI-2, and SCSI-3 A+ Guide to Managing and Maintaining Your PC, Fifth Edition

  11. Bus Width • Narrow SCSI • 8-bit data path • Uses a cable with a 50-pin connector (A cable) • Wide SCSI • 16-bit data path • Uses a cable with a 68-pin connector (P cable) A+ Guide to Managing and Maintaining Your PC, Fifth Edition

  12. Signaling Methods Used on SCSI Cables A+ Guide to Managing and Maintaining Your PC, Fifth Edition

  13. Signaling Methods Used on SCSI Cables (continued) A+ Guide to Managing and Maintaining Your PC, Fifth Edition

  14. Connectors Used with SCSI Cables • Not affected by signaling method used • Types vary in shape and pin density; can be connected with adapters • Two main types: • 50-pin (A cable) • 68-pin (P cable) • Last connector on last device must be filled with a terminator A+ Guide to Managing and Maintaining Your PC, Fifth Edition

  15. SCSI Connectors A+ Guide to Managing and Maintaining Your PC, Fifth Edition

  16. Multiple Connectors on the SCSI Bus A+ Guide to Managing and Maintaining Your PC, Fifth Edition

  17. Termination • Prevents echo effect from electrical noise and reflected data at end of SCSI daisy chain • Required at each end of a SCSI chain A+ Guide to Managing and Maintaining Your PC, Fifth Edition

  18. Ways to Terminate the End of a SCSI Chain • Switch setting on host adapter that activates or deactivates a terminating resistor on the card • Single SCSI connection or two connections • Resistor physically mounted on the device • Internal terminators that turn on or off with a jumper setting on the device • Software-controlled termination A+ Guide to Managing and Maintaining Your PC, Fifth Edition

  19. External SCSI Terminator A+ Guide to Managing and Maintaining Your PC, Fifth Edition

  20. SCSI-1 (Regular SCSI) No common command set 8-bit data bus 7 possible devices SCSI-2 (Fast SCSI) Common command set 16-bit data bus 15 possible devices Mandatory parity checking Major Versions of SCSI A+ Guide to Managing and Maintaining Your PC, Fifth Edition

  21. Major Versions of SCSI (continued) • SCSI-3 (Ultra SCSI) • Supports both parallel and serial data transmission, and FireWire connections • Data transfer of 320 MB/sec (Ultra 320 SCSI) • Support up to 32 devices • Includes SPI standard A+ Guide to Managing and Maintaining Your PC, Fifth Edition

  22. Comparing IDE and SCSI • IDE • May give better performance when using a single disk drive with an OS like Windows 98 or Windows Me • SCSI • Increases performance where heavy load is placed on system and its components • Some OSs include increased support for SCSI features and take better advantage of them • More expensive; better performance A+ Guide to Managing and Maintaining Your PC, Fifth Edition

  23. Considerations When Choosing Between IDE and SCSI Drives A+ Guide to Managing and Maintaining Your PC, Fifth Edition

  24. More SCSI Considerations • Drives perform better in RAID array • Generally provides better performance • Often used on high-demand servers A+ Guide to Managing and Maintaining Your PC, Fifth Edition

  25. Installing a SCSI Hard Drive • Host adapter and cables must be compatible with SCSI drive • Configure SCSI host adapter and SCSI hard drive to communicate with each other: • 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 A+ Guide to Managing and Maintaining Your PC, Fifth Edition

  26. SCSI Hard Drives Connectors A+ Guide to Managing and Maintaining Your PC, Fifth Edition

  27. Hands-on Project: Install a SCSI Device • pp. 1021 A+ Guide to Managing and Maintaining Your PC, Fifth Edition

More Related