NixOS has enjoyed popularity among ZFS users thanks to
its declarative configuration and native ZFS support.
However, the installation guide used hardcoded disk
names in configuration files, which is unnecessary and
is the source of difficulties in multidisk setups.
The guide is now rewritten to leverage expressions in
the Nix language to manage multidisk setups.
Also adds instruction on replacing failed disk.
Closes#385.
Signed-off-by: Maurice Zhou <ja@apvc.uk>
cc6d72c02d