If a drive fails that is part of a software RAID 1 device, your system might not recognize the replacement drive and does not begin remirroring automatically.
Reboot the system to re-scan devices and recognize the replacement drive.
Unmount the NSS volumes on the software RAID device to stop the I/O.
Expand the software RAID 1 device and specify space from the replacement drive as a new RAID segment. Remirroring begins automatically.
Allow the remirror to complete before mounting the NSS volumes.