How to shut down openwrt without corrupting file systems?

What is the preferred way to shutdown the router, without corrupting the files contained on a RAID array or an attached USB drive? Will the halt or poweroff commands perform the necessary steps? Is there a difference between the commands?

Along the same lines, what is the preferred way to eject a USB drive from the router? Is it just a matter of disabling the mount in Luci?

poweroff will sync all file systems and halt the system. there is no shutdown command.

you can unmount from within luci, or with umount /mount/whatever on the command line.