[Unit]
Description=Mirror /srv/nfs (selective) to /mnt/backup (local 2nd copy of critical NFS)
After=network-online.target local-fs.target
Wants=network-online.target

[Service]
Type=oneshot
ExecStart=/usr/local/bin/nfs-mirror
StandardOutput=journal
StandardError=journal
SyslogIdentifier=nfs-mirror
# Heavy sustained IO — don't compete with foreground services.
Nice=10
IOSchedulingClass=idle
TimeoutStartSec=18000