How Booting Into Single-User Mode Affects Mirrors

If a system with mirrors for root (/), /usr, and swap--the so-called "boot" file systems--is booted into single-user mode (boot -s), these mirrors and possibly all mirrors on the system will appear in the "Needing Maintenance" state when viewed with the metastat command. Furthermore, if writes occur to these slices, metastat shows an increase in dirty regions on the mirrors.

Though this appears potentially dangerous, there is no need for concern. The metasync -r command, which normally occurs during boot to resync mirrors, is interrupted when the system is booted into single-user mode. Once the system is rebooted, metasync -r will run and resync all mirrors.

If this is a concern, run metasync -r manually.