It is possible to run multiple instances of the Hurd in parallel, on a single instance of Mach. Other than performance virtualizing these problematic devices., they are essentially isolated. Practically, as many devices do not allow multiple non- users, e.g., hard drive and network this is not currently possible. It can be overcome, however, by
When extra hardware is not available, it is possible to use a sub-Hurd.
Neighborhurd is a pun on neighborhood, and a stance against hierarchies.