Whipple Data Archiving Using DVD-RAM

The Whipple Observatory's 10 m gamma-ray telescope generates roughly 1 GB of data in a single night's observation. These data are archived locally and distributed to several institutions world wide for subsequent reduction and analysis. In the past we archived data on 4mm digital audio tapes (DAT) and compact disks (CDROM). DATs though high in capacity (2 GB per tape), are limited to sequential access and therefore quite slow. In contrast, CDROMs provide random access so are much faster but are limited to 650 MB per volume.


The next generation of optical digital data storage is the digital verstile disk (DVD). As this technology is new, a standard format is yet to emerge. In the mean time, several groups of electronics manufactures have developed their own format in the hope that their hardware becomes the standard. Thus far DVD-R, DVD-RW, DVD+RW, DVD-ROM and DVD-RAM have been introduced. Information about the various formats can be found in the DVD FAQ and a good article about writeable DVD by E-Media Professional.


We decided to go with DVD-RAM because of its large capacity, 5.2 GB on double sided disks (9.4 GB disks are now available) and its re-writable capability. DVD-RAM drives are made by Toshiba, Hitachi, Panasonic and Pinnacle Micro. We purchased the Panasonic LF-D100.

Using DVD-RAM with Linux

The Linux kernel recognizes the Panasonic LF-D100 drive as a read only CDROM device. Your first step will be to patch the kernel to recognize the drive as both CDROM and Magneto Optical device.

Next if you are using a kernel version prior to 2.1.32 you will also have to apply a patch to the scsi drive device (sd.c) to support 2048 bytes/sector drives. Now you should be ready to use your DVD-RAM drive. The DVD-RAM drive will be recognized by kernel as two devices The optical device may be treated as a removal disk. We have successfully archived data to DVD-RAM using a Compaq Alpha running RedHat Linux 6.0.

Universal Disk Format (UDF) - standard DVD filesystems

In order to be able to read a DVD disk on any platform a standard filesystem has been developed called UDF. This performs a function similar to the ISO9660 filesystem structure developed for CDROM technology. I have not yet tried writing a UDF filesystem to DVD-RAM but do not see why dd shouldn't work.