If you would like to back up your data to DVD-R format discs, there are a few obstacles, which must be overcome. It is necessary to make an iso file for input to the DVD-R recording software. This step combined with the disc burning step takes a long time, so it may be impractical to add an additional compression step during a data collection run. The size of the iso file is limited by the operating system, which may be less than the total DVD-R capacity in some cases. Check your system documentation. If you are able to overcome these obstacles, then your data will be preserved in a highly stable and accessible form.

DVD-R discs have a 4.7 gigabyte capacity, but due to file system limitations and variations in disc quality, it may be more practical to use less than 4GB in most cases. If your frames are 1k binned, then this is certainly enough space for 2 data sets of 180 frames each, with room to spare. For unbinned 2k frames, a single pass of 180 frames is over capacity for the DVD-R disc, and the data must be split into parts to fit on two discs. If your single passes are shorter, in the 60-120 frame range, then an unbinned pass will fit on the DVD-R disc with plenty of space for processing files.

Here is a typical backup session, which I tested on the adrenaline GNU/Linux workstation at A1.

If you run into mounting problems, then seek assistance from the staff.

The most common problem that occurs with DVD-R backups is buffer underruns, but given the speed of our network and hardware, this is an unlikely occurance so long as the backup station is not overloaded with other tasks. For a quick check use "ls -R" to list the contents of the disc. The last file in the listing will also be the last file on the disc, where underruns are most likely to appear. If it is an image file, then test it with xdisp. If it is a text file, use "tail". Most non-underrun problems will give obvious reports during cdrecord execution.

Finally a word about DVD-RAM and other formats. DVD-RAM was a great idea which never caught on, probably because the overhead in writing the format is about equal to the iso9660 formats. In other words, it is just as slow as DVD-R in the long run. DVD+R is a new format, which is not as well supported by existing software. DVD-R provides the best compatibility with the millions of DVD movie players that have been sold, so it is very likely to prevail as a standard. Moreover, DVD-R is also the default format of the popular Apple Superdrive, which will soon be available across their whole product line. If you want your data to be accessible in a standard format for years to come, I would recommend DVD-R.

For problems regarding this document, email me.
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