btrfs replace <subcommand> <args>
btrfs replace is used to replace btrfs managed devices with other device.
- cancel <mount_point>
Cancel a running device replace operation.
- start [options] <srcdev>|<devid> <targetdev> <path>
Replace device of a btrfs filesystem.
On a live filesystem, duplicate the data to the target device which is currently stored on the source device. If the source device is not available anymore, or if the -r option is set, the data is built only using the RAID redundancy mechanisms. After completion of the operation, the source device is removed from the filesystem. If the srcdev is a numerical value, it is assumed to be the device id of the filesystem which is mounted at path, otherwise it is the path to the source device. If the source device is disconnected, from the system, you have to use the devid parameter format. The targetdev needs to be same size or larger than the srcdev.
The filesystem has to be resized to fully take advantage of a larger target device; this can be achieved with
btrfs filesystem resize <devid>:max /path
only read from srcdev if no other zero-defect mirror exists. (enable this if your drive has lots of read errors, the access would be very slow)
force using and overwriting targetdev even if it looks like it contains a valid btrfs filesystem.
A valid filesystem is assumed if a btrfs superblock is found which contains a correct checksum. Devices that are currently mounted are never allowed to be used as the targetdev.
no background replace.
wait if there’s another exclusive operation running, otherwise continue
Do not perform whole device TRIM operation on devices that are capable of that. This does not affect discard/trim operation when the filesystem is mounted. Please see the mount option discard for that in btrfs(5).
- status [-1] <mount_point>
Print status and progress information of a running device replace operation.
print once instead of print continuously until the replace operation finishes (or is cancelled)
Replacing an online drive with a bigger one
Given the following filesystem mounted at /mnt/my-vault
Label: 'MyVault' uuid: ae20903e-b72d-49ba-b944-901fc6d888a1 Total devices 2 FS bytes used 1TiB devid 1 size 1TiB used 500.00GiB path /dev/sda devid 2 size 1TiB used 500.00GiB path /dev/sdb
In order to replace /dev/sda (devid 1) with a bigger drive located at /dev/sdc you would run the following:
btrfs replace start 1 /dev/sdc /mnt/my-vault/
You can monitor progress via:
btrfs replace status /mnt/my-vault/
After the replacement is complete, as per the docs at btrfs-filesystem(8) in order to use the entire storage space of the new drive you need to run:
btrfs filesystem resize 1:max /mnt/my-vault/
btrfs replace returns a zero exit status if it succeeds. Non zero is returned in case of failure.
btrfs is part of btrfs-progs. Please refer to the documentation at https://btrfs.readthedocs.io.