Even RAID1 doesn't guarantee this'll work. There are many ways simply disconnecting the secondary drive while cause problems: 1) The app may be in the middle

Even RAID1 doesn't guarantee this'll work. There are many ways simply disconnecting the secondary drive while cause problems: 1) The app may be in the middle of a series of DB commands that all need to complete with success before the DB is consistent at the app layer. 2) The DB is in the process of writing out some table rows and hasn't finished. 3) The DB has written some temporary locks to portions of the database that need to be released. 4) The OS hasn't committed writes from the DB to disk 5) The disk hasn't committed writes from the os to platter yet. Your best bet of this working is to cleanly shut down your app, then cleanly shut down your DB and run an fs sync. After all that it might be ok to yank the drive. Just yanking a RAID1 drive may work sometimes, but I wouldn't count on it. Especially when every DB system I know of has some sort of backup/dump mechanism. As someone else mentioned, RAID is great for providing high availability, but it does not provide disaster recovery.