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Modifying the SCSI / Fibre Channel Block Size

Modifying the SCSI / Fibre Channel Block Size. Presented by Keith Bonneau, John Chrzanowski and Craig O’Brien Advised by Robert Kinicki and Mark Claypool. Project Goals. Edit the Fibre Channel frame to utilize 100% of the payload for data transfer.

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Modifying the SCSI / Fibre Channel Block Size

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  1. Modifying the SCSI / Fibre Channel Block Size Presented by Keith Bonneau, John Chrzanowski and Craig O’Brien Advised by Robert Kinicki and Mark Claypool

  2. Project Goals • Edit the Fibre Channel frame to utilize 100% of the payload for data transfer. • Change the block size of the hard disk to reflect the changes to the frame. • Make these changes transparent to the user and the Linux kernel. • Why?

  3. Storage Area Network (SAN) • Improved reliability. • Better data access and backup. • Flexible Architecture. • Load balancing. • Supports many different protocols. • Superior to direct attached storage.

  4. SAN Overview The specific configuration of the SAN we used for the project.

  5. Fibre Channel • Long cable length up to 10 km. • Transfer speeds up to 2 gbps. • Layered interface. • Data must be sent through frames. • Used as a backbone for most commercial networks.

  6. Small Computer System Interface (SCSI) • Communicates through specific commands. • Limited by cable length, and number of devices. • 25 meter maximum cable length. • 15 devices allowed on the SCSI bus. • Interfaces well with Fibre Channel.

  7. Methodology • Located and modified the driver that detects the SCSI devices. • Compiled the kernel to reflect these changes. • Required a reconfiguration of the Linux kernel and a new image.

  8. Methodology • Performed a low level format on the hard disk to increase its block size from 512 bytes to 528 bytes. • Modified the host bus adapter driver in order to handle the extra 16 bytes being transmitted.

  9. Results Figure 1: Writing to the 512 byte disk Figure 2: Writing to the 528 byte disk

  10. Conclusion • The hard disk needs a firmware update from Seagate. • Upon completion, the resulting data transfer would be more secure. • Relatively no added time or size, making this ideal for streaming media.

  11. Future Recommendations • Read the host bus adapter code and search for alternative modification points. • Add and remove the 16 bytes completely on the SCSI layer. • Request access to appropriate Windows source files to adapt their platform.

  12. Questions?

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