Hitchhiker's Guide to Openbsd

DVD writing speed
It may be useful to point out that DVD speed indications differ from CD-ROM speed indications. The 
following table gives an overview: 
DVD read/write speed Transfer rate (MB/s) Equivalent CD-R(W) read/write speed
1x
1.32
9x
2x
2.64
18x
4x
5.28
36x
8x
10.57
72x
As can been seen from the table, the transfer rates are relatively high, and you should check whether 
your bus (SCSI, (E)IDE/ATAPI, USB) is performant enough to handle this throughput. Especially the 
older USB 1.0 and 1.1 interfaces work at slower transfer rates, with maximal rates of 1.5 Mbit/s and 12 
Mbit/s, respectively. That means USB 1.0 has a maximal throughput of 178.8 kByte/s and USB 1.1 has a 
maximal throughput of 1.43 MB/s. USB 2.0 is much faster: 480 Mbit/s or 57.2 MB/s. In general, the 
speed of SCSI and (E)IDE/ATAPI buses should be just fine. 
Writing the DVD
Basically, the process is very similar to writing CD-R(W)s. The software used, however, is different. At 
the moment, the best option is growisofs from the 
sysutils/dvd+rw-tools
package. This utility 
writes an ISO 9660 image to the DVD medium. All recordable DVD formats are supported by the dvd
+rw-tools. 
In case you want to find out more info about the media in your DVD writer (for example if you lost the 
info label in the jewel case or are just disorganized like me), you can use the dvd+rw-mediainfo utility. 
There are two options to write the DVD: 
●
Pre-master an ISO 9660 from your data, storing the image on your hard disk; then write this 
image to the DVD. 
●
Write an ISO 9660 from your data immediately to the DVD. 
I created a pre-mastered ISO 9660 image from the OpenBSD CVS modules (src, xenocara, ports and 
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13 - Multimedia
www) contained in the /cvs directory on my disk. I used the following command, which looks very 
similar to the one I used to create the CD-ROM image above. 
$ mkhybrid -r -o cvs.iso /cvs
If desired, check the ISO 9660 filesystem by 
mounting the image
. To write this image (about 2 GB) to 
an empty DVD disc, one could use: 
# growisofs -dvd-compat -Z /dev/rcd2c=cvs.iso
Executing 'builtin_dd if=cvs.iso of=/dev/rcd2c obs=32k 
seek=0'
/dev/rcd2c: pre-formatting blank DVD+RW...
/dev/rcd2c: "Current Write Speed" is 4.1x1385KBps.
23822336/1545832448 ( 1.5%) @3.9x, remaining 5:19
42172416/1545832448 ( 2.7%) @3.9x, remaining 5:20
60522496/1545832448 ( 3.9%) @3.9x, remaining 4:54
...
1504706560/1545832448 (97.3%) @3.9x, remaining 0:07
1523318784/1545832448 (98.5%) @3.9x, remaining 0:04
1541898240/1545832448 (99.7%) @3.9x, remaining 0:00
/dev/rcd2c: flushing cache
/dev/rcd2c: writing lead-out
/dev/rcd2c: reloading tray
The 
-Z
option tells growisofs to burn an initial session to the device, which in this case is my DVD 
writer, attached to cd2. The 
-dvd-compat
option closes the disk, which means no more sessions can 
be appended to it. This should provide better compatibility with video DVD players and some older 
DVD-ROM units. 
Notice how growisofs indicates the writing speed, in this case 3.9x DVD speed, which is what could be 
expected from the media and writer combination, as indicated by dvd+rw-mediainfo. 
If you are short on disk space and cannot store an ISO 9660 image for a DVD, you can write your data 
directly to the DVD. Let's first do a dry run, which simulates the creation of the filesystem. 
# growisofs -dry-run -Z /dev/rcd2c -R /cvs
If this succeeds, just leave out the -dry-run option and start burning the DVD. 
# growisofs -Z /dev/rcd2c -R /cvs
It is also possible to append data to an existing DVD, by using the -M option, which merges a new 
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session to an existing one: 
# growisofs -M /dev/rcd2c -R /mydata
For more information about growisofs, refer to the manual page. 
When you have finished writing the DVD, mount it and see whether everything you expected to be 
there, is indeed there.