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Hi Pavel,

On Tue, Oct 11, 2005 at 10:39:16AM +0200, Pavel Cahyna wrote:
> Wouldn't it make sense if other drivers having larger sectors did the
> same? Why can't DVD/CD+-(M)R(W) do read-modify-write?

technically they can, though the penalties are huge.

1) switching from reading to writing and back take typically 
   takes significant time in the order of about *half a second* on a 
   switch.

2) you will loose sectors when writing on recordables. This results in a 
   few logical sectors NOT being adressable anymore. I dont have to tell 
   you what an administrative mess this gives on allocation.

3) CD-MRW and DVD+(M)RW are the only ones that allow you to write a *single
   sector*. Others even require a whole ECC block to be written forcing a 
   read/modify/write cycle itself if not in cache so the filingsystem 
   implementation needs to be optimised to minimise this as much as 
   possible or performance will be very bad.

Cheers,
Reinoud

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