18.10 Replacing Devices on a Live File System

Note

The device replacement feature requires that you boot the system using UEK R3.

You can replace devices on a live file system. You do not need to unmount the file system or stop any tasks that are using it. If the system crashes or loses power while the replacement is taking place, the operation resumes when the system next mounts the file system.

Use the following command to replace a device on a mounted btrfs file system:

# btrfs replace start source_dev target_dev [-r] mountpoint

source_dev and target_dev specify the device to be replaced (source device) and the replacement device (target device). mountpoint specifies the file system that is using the source device. The target device must be the same size as or larger than the source device. If the source device is no longer available or you specify the -r option, the data is reconstructed by using redundant data obtained from other devices (such as another available mirror). The source device is removed from the file system when the operation is complete.

You can use the btrfs replace status mountpoint and btrfs replace cancel mountpoint commands to check the progress of the replacement operation or to cancel the operation.