The role and design of the DOMS system, our metadata storage system
DOMS is based on a Fedora 3 repository system.
Bitpreservation for the DOMS system is an issue we need to handle. Principally speaking, DOMS does not handle bit preservation. For this requirement, we have the excellent system called the Bit repository.
The fundamental problem is, that content in DOMS, even with the tape system detailed above, still only exists as one copy, and is thus vulnerable to a number of system failures. So, our strategy is to ensure that the content exist in more than one copy.
We have two ways to ensure this.
Fedora journaling is described here https://wiki.duraspace.org/display/FEDORA36/Journaling. It is a standard, if not widely used, component of the Fedora repository system, and one we could be use without much developing work.
The problem with using a journaling fedora is ensuring that the two servers are identical. While the journaling system SHOULD ensure identicallity, actually testing it would be difficult. Due to this problem, we have decided not to use journaling as a solution to bit preservation. We have not ruled out using journaling as a means for load balancing for read operations, thus that is a discussion for another day.
The tapes, detailed above, have a very nice quality. When a tape is closed for writing, it will never be updated again. This means that we can archive this tape in the bitrepository. As soon as the tape is ingested into the bit repository, we know that the content is stored in multiple copies.
The tapes have been designed so that, if any content have been written to a tape, it will be closed after a set time. This way, we can ensure that any content added to DOMS will be taped and ingested in the bit repository within a time frame.
To build this solution, we need to develop a simple component, detailed HERE.