Question: Disk Mirroring preceding RAID?

From: Stan Sieler <>
Date: Mon Dec 4 15:19:01 2000

> Sounds like a patent suit :-)

No...just an argument, really! (I'd mention if it was patent

> This is kind of a specious argument. There were volume shadowing (aka
> hardware mirroring) products available before people started calling it
> "RAID" and in fact the IBM DASD farms could do volume shadowing and it
> isn't "RAID" because RAID is "Redundant Array of *Inexpensive* Disks" and
> 3380's certainly weren't "inexpensive."

I dug up a copy of the original RAID article: "A Case for Redundant Arrays
of Inexpensive Disks (RAID)" by Patterson, Gibson, and Katz (from June,

They must have trained to be patent lawyers, because their definition
of RAID is verrrry broad! (To the point where software implemented
mirroring would still be called RAID1.)

Basically, I found that if I tried to forget that RAID was an
acronym with a meaning, I can see how people claim that any and all
disk mirroring is a form of RAID ... even if the mirroring preceded
the name "RAID".

BTW, I found a reprint of the article in "Readings in Computer
Architecture", edited by Hill, Jouppi, and Sohi,
published in 2000 by Morgan Kaufmann. This is a great reference
book. Articles include:

   Architecture of the IBM System/360; by Amdahl, Blaauw, & Brooks

   Parallel Operation in the Control Data 6600

   The Cray-1 Computer System

   Cray-1 Computer Technology

   Cramming More Components onto Integrated Circuits; by Gordon Moore

wait...maybe there's a web site...

  Chapter 1 - Classic Machines: Technology, Implementation, and Economics
  Chapter 2 - Methods
  Chapter 3 - Instruction Sets
  Chapter 4 - Instruction Level Parallelism (ILP)
  Chapter 5 - Dataflow and Multithreading
  Chapter 6 - Memory Systems
  Chapter 7 - I/O: Storage Systems, Networks, and Graphics
  Chapter 8 - Single-Instruction Multiple Data (SIMD) Parallelism
  Chapter 9 - Multiprocessors and Multicomputers
  Chapter 10 - Recent Implementations and Future Prospects

Highly recommended!

Stan Sieler
Received on Mon Dec 04 2000 - 15:19:01 GMT

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