DVD newbie - which format should I use?

[Helmut Jarausch <jarausch@igpm.rwth-aachen.de>]

Hi,
I've tried to search the archive and various FAQs but I more confused
than before.

I've just bought my first DVD burner (LG GSA-4167B) which supports
several DVD formats. I've burnt my first DVD-R disc which succeeded
but a bit slow. cdrecordProDVD reported  "DMA speed to slow) (OK for 8x)
but then the average write speed was only 1.5x ( for a chunk of 3.6Gb).
Is there any explanation for this?

Second and most important, which media (format) should I use.
I need my DVD burner for backup only, so I don't need compatability
with any DVD-ROM. I do need multi-session capability since my
backups are not always 4.4 GB.

Many thanks for a hint or pointer to a FAQ

Helmut Jarausch

Lehrstuhl fuer Numerische Mathematik
RWTH - Aachen University
D 52056 Aachen, Germany