If we are mounting the btrfs volumes from the /etc/fstab file, we need to ensure that a btrfs scan is effected before we mount the /data/simple directory. This will locate all the devices that participate within the volume. The initramfs file system can complete this task for us on a later system including RHEL 7. If your existing filesystem was already using btrfs, the scan will be built-in your current initramfs. If btrfs is new to your system, you will need to generate a new initial RAM disk. Make sure that you use the correct initramfs and kernel version for your system when running the following command:

# dracut -v -a btrfs -f /boot/initramfs-$(uname -r) /boot/vmlinuz-$(uname -r)

We can then add an entry into the /etc/fstab file similar to the following:

/dev/sdd  /data/simple  btrfs  defaults  0 0