Add ZFS support

[erik78se]

I'd love to be able to see ZFS information in this dashboard aswell.

I'm using the prometheus-node-exporter and get values for my zfs like this:

I don't know how to add it myself but I'm happy to test it and provide feedback etc.

node_zfs_zpool_rupdate{zpool="default"} 9.43295729695335e+14
node_zfs_zpool_rupdate{zpool="juju-zfs"} 7.70109311615835e+14
# HELP node_zfs_zpool_state kstat.zfs.misc.state
# TYPE node_zfs_zpool_state gauge
node_zfs_zpool_state{state="degraded",zpool="default"} 0
node_zfs_zpool_state{state="degraded",zpool="juju-zfs"} 0
node_zfs_zpool_state{state="faulted",zpool="default"} 0
node_zfs_zpool_state{state="faulted",zpool="juju-zfs"} 0
node_zfs_zpool_state{state="offline",zpool="default"} 0
node_zfs_zpool_state{state="offline",zpool="juju-zfs"} 0
node_zfs_zpool_state{state="online",zpool="default"} 1
node_zfs_zpool_state{state="online",zpool="juju-zfs"} 1
node_zfs_zpool_state{state="removed",zpool="default"} 0
node_zfs_zpool_state{state="removed",zpool="juju-zfs"} 0
node_zfs_zpool_state{state="unavail",zpool="default"} 0
node_zfs_zpool_state{state="unavail",zpool="juju-zfs"} 0
# HELP node_zfs_zpool_wcnt kstat.zfs.misc.io.wcnt
# TYPE node_zfs_zpool_wcnt untyped
node_zfs_zpool_wcnt{zpool="default"} 0
node_zfs_zpool_wcnt{zpool="juju-zfs"} 0
# HELP node_zfs_zpool_wlentime kstat.zfs.misc.io.wlentime
# TYPE node_zfs_zpool_wlentime untyped
node_zfs_zpool_wlentime{zpool="default"} 3.72872119814169e+14
node_zfs_zpool_wlentime{zpool="juju-zfs"} 1.48531534e+08
# HELP node_zfs_zpool_writes kstat.zfs.misc.io.writes
# TYPE node_zfs_zpool_writes untyped
node_zfs_zpool_writes{zpool="default"} 4.8604624e+08
node_zfs_zpool_writes{zpool="juju-zfs"} 272
# HELP node_zfs_zpool_wtime kstat.zfs.misc.io.wtime
# TYPE node_zfs_zpool_wtime untyped
node_zfs_zpool_wtime{zpool="default"} 2.0000341084942e+13
node_zfs_zpool_wtime{zpool="juju-zfs"} 7.922821e+06