Servers can be hardware (physical) or software (virtual) based.
Multiple software based servers can exist on one or shared across multiple physical servers across multiple locations.
This is called virtualisation or multi-tenanted architecture.
Each virtual server may be owned by the same or different companies. That is, physical server or servers may be shared with other companies in multiple locations.
The greater the number of shared servers and information locations, the greater the risk.
Virtualisation is often used in cloud computing.
Adapted Ernst (2013)