Uncompressed DDS-format 4mm DAT tape was chosen for archival output.
There is no particular justification for why we chose this medium over
any other (although we also considered using a CD-ROM writer) and we
may change if we find reason to do so. We were unable to find any
studies suggesting that a particular medium was significantly more
reliable or suitable to this purpose than any of the
The tapes are being written out using the TCFS standard, but a number of parameters remain unspecified in the standard. For instance, TCFS doesn't specify a blocking factor to use for the output. We happened to arbitrarily choose 10-kilobyte blocks, since the performance concerns over blocking factor are largely irrelevant in the DDS format. We also chose to put an end-of-file (EOF) mark at the end of each old tape's worth of data. This, again, was a totally arbitrary decision; our hope is that the EOF mark will make searching the tape easier, but it is unclear that the mark will provide any performance benefits. These issues remain unspecified in the format because TCFS is completely self-delimiting and therefore insensitive to record length and EOF marks.
To reduce further data loss in the future, we are simultaneously making two copies of the tape on output. Neither of these two tapes will be publicly available, and any publicly available tape would be a third copy (once the privacy issues are settled). One set of these tapes will be stored at the lab, for any of the purposes mentioned in the introduction. Another set of these tapes will be placed in off-site environmentally controlled storage for posterity.
The original media will not be destroyed outright, but we will be less stringent in the care and handling of these ``dead'' tapes. They will probably be sent to off-site storage, but their eventual fate is unknown and will depend on financial constraints. There is no good reason for us to dispose of the old tapes, and no expedient way for us to recycle them. It may also be the case that any particular file that we were unable to reconstruct from these tapes during this project will be of such extraordinary interest to future generations to justify the heroic efforts required to rescue the data.
Some have suggested that a continuous path for file migration from
disk to robotically-accessed media (media jukeboxes) to off-line media
is the ideal