コンピューター・アーキテクチャ
Computer Architecture

Outline of This Lecture

• What's a Disk Drive?
• The Importance of a Disk Drive
• The Access Time Gap
• The Insides of a Disk Drive
• Disk Drive Trends
• The Basics of a Bus
• A Little History
• Homework

A disk drive stores data in sectors that held on tracks; all of the tracks at the same distance from the spindle are called a cylinder.

It uses a read/write head attached to a slider, mounted on an actuator arm, to read and write the data as it spins past.

In an architectural sense, what's important about disk drives?

• They are expensive
• They consume lots of power
• They are often the performance bottleneck (the access time gap)
• They break more easily than many other parts of the system

...and yet, the Information Revolution （情報革命？） can fairly be said to be built on disk drives. Without them, there would be no PCs, no Google.

• A Bus is Shared Bandwidth
• Requires Addressing
• Bus Transactions
• Arbitration: Priority, Fairness
• Limitations in Width and Length
• Types of Buses: Memory and Peripheral
• Standardization

The very first hard disk drive, the RAMAC, from IBM (1956):

1. This table contains a lot of information on many disk drives from 1975 to 1997, but none since. Pick any recent disk drive and fill in the information.
2. For the disk drive you have picked, calculate:
   1. How long it will take to read the entire disk sequentially?
   2. How long it will take to read the entire disk one 512 byte sector at a time, in random order?
3. Who controls the specification for each of these types of buses?
   1. Frontside bus
   2. Memory bus
   3. PCI
   4. SCSI

Next Lecture

Next lecture:

第12回 1月6日 RAID: ストレージの並列と安全性
Lecture 12, January 6: RAID: Parallelism and Protection in Storage Systems

• Follow-up from this lecture:
  • P-H: Chapter 8
  • H-P:
• For next time:
  • P-H: Chapter 8
  • H-P: Chapter 6

Additional Information

• Columbia page on the RP06
• INWAP page on TyMSHARE systems
• Good photos at Electronetwork
• A good comic
• Still more good photos at darkroastedblend
• An old paper of mine (USENIX, 1997)
• More results on zoning in disk drives
• An IBM page on GMR
• Nobel Prize for GMR
• Class top page
• Elsevier's web page for the textbook.
• My web page on system software.

その他

• Rodney Van Meterのホームページ
• 徳田・村井・楠本・中村・高汐・重近・湧川・バンミーター研究プロジェクト