Once the DRBD resource is running and in the primary role (and potentially still in the process of running the initial device synchronization), you may proceed with creating the filesystem for MySQL data. XFS is the generally recommended filesystem:
mkfs -t xfs /dev/drbd0
You may also use the alternate device path for the DRBD device, which may be easier to remember as it includes the self-explanatory resource name:
mkfs -t xfs /dev/drbd/by-res/mysql
Once completed, you may safely return the device to the secondary role. Any ongoing device synchronization will continue in the background:
drbdadm secondary mysql
