Fibre Channel RAID Array

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Fibre Channel RAID Array

• Bob Kulzick
• Koray Sahin

2
Fibre Channel

• High speed network protocol
• Loop topology
• Benefits
• High speed, bandwidth (1-2Gbps)
• Modular
• Long distance (10km optical, 30m copper)
• Hot-swap capable
• Expandable (126 devices per loop)
• Reliable, fault tolerant

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Use of FC with Hard Drives

• FC used as a medium to communicate with SCSI
  devices
• Transparent to SCSI devices
• Superior performance to SCSI interconnect
  standards

4
RAID

• Redundant Array of (Inexpensive) Independent
  Disks
• Increase throughput without increasing speed
• Many Modes
• Raid 0
• Raid 1
• Raid 5
• Software vs. Hardware

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Motivation

• IDE Price/Performance Doldrums
• Integrated Drive Electronics
• Small Computer Systems Interface
• Fiber-Channel
• Raid
• Speed
• Reliability
• Unexploited Demographic

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Objectives

• Create a RAID array of 8 fiber channel hard
  drives.
• Hot-swapping
• Raid 5
• 2Gbps (1GHz) operation
• Fault Tolerant
• Inexpensive

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Original Ideas
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Proposed Design 1 Modular Software RAID
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Proposed Design 2Direct Software RAID
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PCB Redesign

• Cleaner layout
• More robust
• Improved transmission lines
• Tighter coupling
• Controlled impedance
• More consistent spacing between traces
• Elimination of solder mask
• Consistent trace widths
• Reduction of discontinuities (bends, vias, etc)
• Better ground-plane coverage
• Equalized line lengths
• Proper termination

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Transmission Line Simulation
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TDR Measurements

• Time Domain Reflectometry
• Measures inconsistencies on transmission lines
• Also can be used to determine impedance mismatch
• Used to verify TL integrity and check matching
• Adjusted matching networks as a result

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Hot-swap Capability

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Linux Issues

• Antiquated Driver
• Redhat 6.2 vs. Redhat 8.5
• Drive Formatting
• Block Drivers
• Kernel Interfacing

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Raid Tests

• Existence
• Copying a File
• Raid 5
• Single Drive Failure
• Double Drive Failure

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Challenges and Successes

• Hardware Challenges
• Signal integrity on Transmission lines
• High speed relays
• Characterizing TL impedance / designing matching
  networks
• Hot-swapping
• Amplification of signal
• Successes
• Achieved good signal quality, drives detect and
  function properly
• Work on hot swapping in progress

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Challenges and Successes cont.

• Software Challenges
• Education
• Overabundance of Resources
• Open Source Model
• Software Successes
• Driver installation
• Raid 5