Man pages matching name nfsiostat in section 8:

nfsiostat.8.en	debian 10 / nfs-common
nfsiostat.8.fr	debian 11 / manpages-fr
nfsiostat.8.en	debian 11 / nfs-common
nfsiostat.8.fr	debian 12 / manpages-fr
nfsiostat.8.en	debian 12 / nfs-common