Re: DVD+/-R writers
> Going by my own observation and not what someone tells me, it seems random
> access write to DVD+RW is rather easier than to DVD-RW. I don't have to
> blank the disk, and it still works at 0.1x speed. Andy's DVD+RW kernel patch
> isn't meant for DVD-RW - could this be because DVD-RW doesn't allow
> something?
DVD+RW kernel patch relies on DVD+RW capability of truely random write
access with 2KB granularity. This means that a) required modification to
block driver are truely minimal and trivial; b) no file system code
modifications are required to make arbitrary file system work with
DVD+RW. Also note that random write access is possible for *full* media
capacity *instantly* after *minimal* formatting procedure, which takes
less than minute.
As for DVD-RW on the other hand. If *minimally* formatted for Restricted
Overwrite, DVD-RW still can be recorded only *sequentially*. This makes
it virtually impossible to use *minimally* formatted DVD-RW media for
housing of live read-write file system. Only once fully formated (which
takes 1 hour for 1x media), DVD-RW permits for random write, but with
32KB granularity. Latter means that you either have to have special
kernel driver which would arrange for 32KB granularity or modify file
system code to do same thing. Now note that no work (at least no visible
outcome so far) has been done to accomplish either of these two
alternatives under Linux (or any other Unix implementation), [presumaly]
because it's damn hard. A.
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