The automatic defragmentation built into Mac OS X works only on read-only files that are less than 20 MB in size and in more than eight pieces (which means that their pieces, called “extents”, are now recorded in the Extents B-Tree portion of the disk directory, which Apple calls the Extents Overflow File). The files that are most important to you, which you cannot replace by running an installer, are the ones you yourself created. Not one of these files is “read-only.”

I tried to refer to the original description of these limitations in my own article, “Why Defrag?” in the Tips and Hints forum of the MacFixitForums. I nearly fell out of my Aeron chair when I was automatically directed to a certain subsidiary of CBS.

I once met Bill Stumpf, who, along with Don Chadwick, designed the Aeron chair, while he was setting up slides before a panel discussion. I mentioned to him that no matter how famous one becomes, it is still necessary to set up one’s own slides. He laughed, and confirmed my observation. During the panel discussion, whenever the panel was stumped (sorry for the pun), Bill would apologize for monopolizing the discussion, and would then offer his insightful and unique observations.

During the discussion, a problem arose about the distribution of ice water. Bill Stumpf insigtfully solved the problem in real time, while drawing a minimum of attention to himself. In the back of the audience were two executives from Herman Miller, the manufacturer of the Aeron chair. Anyone with any insight whatsovever could read their facial expressions, which said, “There’s our man.”

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