KB450192 - Replacing a boot drive within a mirrored RAID on FreeNAS https://knowledgebase.45drives.com/kb/kb450192-replacing-a-boot-drive-within-a-mirrored-raid-on-freenas/
KB450192 - Replacing a boot drive within a mirrored RAID on FreeNAS
Posted on December 19, 2019 by Rob MacQueen
Open your FreeNAS UI in a browser.
From the System tab, select Boot
Click the Status button
Select the drive that is currently UNAVAILABLE
Click the the Replace button
Select the appropriate device from the Member Disk drop down and click Replace Disk