All archived images are stored in uncompressed TIF format. TIF (or TIFF) format allows the inclusion of a metadata tag in every image that does not affect the image information itself. At present TIF is considered the most widely compatible and easily transferable file format for images. Longevity of the file format is constantly monitored.
DIAMM images are archived at two locations: the Oxford Hierarchical File Server, managed by OUCS in Oxford, and the Arts and Humanities Data Service in London. Both these archives have secure off-site backup that is updated every 24 hours. Many newly-created archives use, or plan to use, CD or DVD discs for the long-term storage of their data. This is NOT an archive, and will almost certainly result in data loss. The shelf-life of CDs or DVDs is anything from 2 years upwards, but discs can fail before that because they are extremely vulnerable to damage. CD or DVD juke-box systems are completely inappropriate for long-term archiving strategies. The minimum requirement for archiving is a hard-drive RAID system, with off-site secondary backup. Even this is not necessarily sufficient for an important collection of data where the archive is the only repository. Management of a proper storage archive requires a dedicated staff, temperature controlled environment for the systems, and constant monitoring and upgrades. If you are creating a data archive, please contact the Arts and Humanities Data Service for advice about creating a secure long-term archive for your materials.
The OUCS Hierarchical File Server (HFS) system can only be accessed by project staff. It is not accessible via the internet, nor can it be accessed by any registered user of the web portal. The Archive is entirely independent of the web portal, and provides a secure storage system for all the full-size uncompressed images that have so far been captured by DIAMM or its partners, as well as those that have undergone digital manipulation work to restore them to readability. It is purely a storage facility: the images are not used for standard working, and once archived are only accessed again to upgrade format when that becomes necessary (it has not yet been necessary to do this, as TIF format is both stable and universally used). Because it is not a working copy of the images, the HFS content is described as a Dark Archive.