[MacDV] Re: more about the inutility of defragmenting an OS X FS.

[James Asherman]

On Wednesday, December 31, 2003, at 04:23  PM, James Asherman wrote:

>
>>
>> You don't and can't know how the blocks are laid out on physical 
>> disk.  You can't know it  because that information doesn't leave the 
>> disk controller.  The controller maintains a fiction of putting the 
>> blocks where you ask, but it actually puts the blocks wherever it 
>> wants to.  (And the algorithms that the controller uses in its 
>> attempts to optimize logical block placement are highly guarded 
>> secrets, too). The nice GUI maps can only show you the fiction, not 
>> the physical on-platter reality.  For that reason alone, rearranging 
>> disk blocks to make the map look pretty, does nothing for >> performance.
>
> I',
> m
> not stupid. I know how a disc works and what are the illusions and 
> what are the realities.
>  The reality is we need 10's of gigs all ina row so that we miss not 
> 1/60th of a second of video looking for someplace new to put it. And 
> when playing it back after messing with it (more files distributed by 
> the software and discs)  the demand for fast location and processing 
> is even more important. My stuff has to deliver 3.6 megabytes PER 
> SECOND of carefully sequenced material in a continuous stream for two 
> hours. IT gotta be clean man!
>