Re: DVD+/-R writers
> >> > 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.
> >>
> >> So DVD+RW drives do things in firmware what you need to do in the kernel
> >> if you like to have 2k granularity with DVD-RW. But this is nothing a new
> >> firmware could not support.
>
> >Specifications are very explicit about I/O granularity in DVD-RW
> >Restricted Overwrite mode. You seem to be willing to bend standard to
> >suit you, it's not fair play. Secondly it doesn't really matter what one
> >*could* *possibly* do [to stretch something to something else], does it?
>
> Well, it seems that you make unproven assumptions on the quality of DVD+, so
We *both* have only one way to prove our statements: take vendor's word
and try to refute it by practical experience. If vendor's word holds the
scrutiny, then it's considered to be proven. Now, when I say that DVD+RW
implementations provide for 2K granularity and true random access after
minimal formatting procedure, I'm not just repeating something I've
read, I speak from practical experience, both my personal and of several
users.
> I believe that it is fair to tell people that in theory it would be possible to
> enhance DVD- firmware
Yes, it's obvious that it's *theoretically* possible to implement 2KB
write granularity in firmware [once again, which would violate DVD-Forum
specification].
> and hardware
^^^^^^^^^^^^?
> so partially formatted media may be adddressed ramdomly.
Well, once you call my statements unproven, I think I can demand proof
for this one of yours. Prove it to us, that *minimally* formatted DVD-RW
media can be written to in truly arbitrary order. Or at least explain
why there is no implementation, which would actually provide for this.
> >> Note that the kernel also first reads a 512 byte sector from a hard disk
> >> if you like to write only 64 bytes.
>
> >Yes. But as already implied, if you want to extend this to 32KB to
> >accomodate DVD-RW Restricted Overwrite, you have to modify kernel file
> >system driver. The question was "why is there random access possibility
> >for DVD+RW, but not for DVD-RW?"
>
> If you believe that the kernel filesystem driver needs to be modified, then
> you are taling about a broken OS.
Oh! You must be implying that I'm referring to Linux. Well, I'm not. I'm
referring to a typical OS and we can speak about Solaris if you wish.
Have you ever tried to build a file system under Solaris with logical
block larger than 8KB? Try! And before you start arguing that it's
user-land mkfs_* which set this limit. Yes, user-land tools set the
limit, *but* for damn good reason. Because the limit is hardcoded into
filesystem kernel drivers as well [I've examined ufs and udfs code].
This is [*one* of the reasons] why I wrote "you have to modify file
system code."
> On a typical OS, the filesystem code talks to the block abstraction layer.
>
> This layer has been the buffer case on historic implementation and is the
> semgment driver layer + VM Cache in modern implementations.
> What you have to do is to change this layer to know that there may be
> 32 KB Blocks.....
The question was "why is there random access possibility for DVD+RW, but
not for DVD-RW?" The question also was in certain context and can as
well be rephrased as "why is there possibilty for random access of
DVD+RW under Linux now, but not for DVD-RW?" Your answer essentially is
"there is random access possibility for DVD-RW as well, *if* one a)
modifies unit firmware, b) modifies unit hardware(!), c) modifies OS VM
cache." Pure children's game... A.
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