Review: Reed-Solomon Codes
Motivation: Who Cares About I/O?
I/O Systems
What is a bus?
Advantages of Buses
Disadvantage of Buses
The General Organization of a Bus
Master versus Slave
Types of Buses
A Computer System with One Bus: Backplane Bus
A Two-Bus System
A Three-Bus System (+ backside cache)
The move from Parallel to Serial I/O
Main components of Intel Chipset: Pentium 4
How does the processor actually talk to the device?
Example: Memory-Mapped Display Controller
Hard Disk Drives
Historical Perspective
Disk History
Disk History
Seagate Barracuda
Properties of a Hard Magnetic Disk
MBits per square inch: DRAM as % of Disk over time
Nano-layered Disk Heads
Disk Figure of Merit: Areal Density
Newest technology: Perpendicular Recording
Disk I/O Performance
Magnetic Disk Characteristic
Disk Time Example
Typical Numbers of a Magnetic Disk
Introduction to Queuing Theory
Background: Use of random distributions Memoryless
A Little Queuing Theory: Mean Wait Time
Mean Residual Wait Time: m 1(z)
A Little Queuing Theory: M/G/1 and M/M/1
A Little Queuing Theory: An Example
Use Arrays of Small Disks?
Array Reliability
Redundant Arrays of Disks
Redundant Arrays of Disks RAID 1: Disk Mirroring/Shadowing
Redundant Arrays of Disks RAID 5+: High I/O Rate Parity
Problems of Disk Arrays: Small Writes
System Availability: Orthogonal RAIDs
System-Level Availability
Utility-based Infrastructure
GUID 2
Peer-to-peer systems can be very stable
The Path of an Ocean. Store Update
Archival Dissemination of Fragments
Aside: Why erasure coding? High Durability/overhead ratio!
Conclusion
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