"Mirroring of sites occurs for a variety of reasons.
* To preserve a website or page, especially when it is closed or is about to be closed.
* To provide access to otherwise unavailable information. For example, when the popular Google search engine was banned in 2002 by the People's Republic of China, the mirror elgooG was used as a way of effectively circumventing the ban.
* To preserve historic content. Financial constraints and/or bandwidth prevent the maintainers of a server from keeping older and unsupported content available to users who still may desire them - a mirror may be made to prevent this content from disappearing."
And from the Mirror pop-ups, which I personally witnessed,
“Archive Enclave: Directory
1.1-3.3 Digital Backup Library
3.4-3.5 Terran Artifacts
4.1 Theories of the EVE Gate
5.1 Talocan Technology
6.1-6.9 Emergent Ideologies”
“Communications Enclave: Directory
1.0 - 5.1 Microvirtual Transmission Sensors
5.2 - 5.5 Sensor Backup Systems
6.0 Operation Servers
7.0 Proliferation News Network Studios
8.0 Detransmission Clusters”
“Medical Enclave: Directory
1.0 Emergency
2.0-2.8 Triage
2.9 Stasis
3.0 Quarantine Sector A
4.0 Quarantine Sector B
5.0-9.2 Quarantine Sector C
9.3 Quarantine Sector X”
“Oruze Enclave: Directory
1.0 Solar Engineering
1.1 Photoelectrical Engineering
1.2 Thermovoltaics
1.3 Residential
1.4 Residential”
“Research Enclave – Biogenetics: Directory
1.0-3.2 Animal Cryogenetic Research Laboratories
3.3-3.8 Holding Pens
4.0-6.0 De-animation Genealogy Research Library
7.0-8.0 Student Classrooms
9.0 Human Cryogenetic Applications”
“Research Enclave – Theoretical Genetics: Directory
1.0 Interdigital Neural Activity Laboratories
2.0 Multiple-Ancestry Research
3.0 Statistical Proliferation Archive
4.0 Datagenesis Procedures
5.0- 8.0 Backup Servers
9.0 Mixed Intelligence Displays”
“Research Enclave – Virtual Genetics: Directory
1.0 Neurodegenerative Case Studies
2.0 Non-natural Teleology
3.0-4.7 Test Clinics
4.8 Bioinformatics Archive
4.9 Virtual Mutation
5.0-9.8 Emergent Systems Design”
“Security Enclave: Directory
1.0 Virtual Kinetic Research
2.0 Artificial Intelligence Perpetuation Technology
3.0-5.0 Interstellar Surveillance Task Force
6.0 Anti-Thermocryogenesis Research and Implementation
7.0 Modulation Navigation Network
Essentially, a mirror contains everything you need in case you need to restart a website or server, or access it if it is down. It compiles a 'state' of the system as a snapshot of its activity.
Now, in the context of the EVE universe, this could mean for the Sleepers, a means of storing their technology, knowledge and civilization, a snapshot in time, for later access or upload. Essentially, a civilization-in-a-box.
More importantly, it might mean they are archiving information or data in the view of a possible future catastrophe, from which the universe as a whole will need to recover.