Jan Engelhardt wrote:
Yes. A 650 MB *CD*-RW (DVD-RW too?) formatted in packet mode only has like
500-something megabytes to allow for the sort of seeks required.
On DVD+RW, you get the full 4.3 GB (4.7 gB) AFAICS.
DVD-RAM physically is formatted like a hard disk. It is broken up into zones
that hold different numbers of sectors which are individually and randomly
read/writable. CD/DVD+-RW media is organized as a single long groove that
consists of an unbroken series of large blocks composed of small blocks with
user and control data interleaved and error corrected. It is for this reason
that historically it could only be recorded from start to finish in one pass.
There are two modern techniques to allow pseudo random write access for all
forms of CD/DVD +/- RW media. These are packet mode, and mount rainier mode.
MRW mode formats the disk into 32 KB blocks made up of 2048 byte sectors which
are individually writable as far as the OS knows, because an MRW compliant
drive is required to internally handle any required read/modify/write cycles to
update the 32 KB blocks. MRW mode also reserves some of the disk for sector
sparing which the drive firmware also handles. MRW mode is typically used on
dvd+rw media. IIRC, this format typically "wastes" about 10% of the capacity of
the medium.
I doubt that. 10% of a 4.3 GB disk are, well, roughly 430 MB, which would
make df show 3.9 GB as mountpoint size, not 4.3 GB. [MB and GB are powers
of 1024 here.]
Was that DVD recorded MtR or packet?
--
-bill davidsen ([email protected])
"The secret to procrastination is to put things off until the
last possible moment - but no longer" -me
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