Unfortunately, it is not possible to do either one.
Once you create /dev/drbd0 on both DB Servers, you have to mount the DRBD Primary on a folder. That folder cannot have anything with active file handles. The protocol I use is:
drbdadm primary drbd0
mount /dev/drbd0 /var/lib/mysql
service mysql start
You want DRBD to house MySQL Data. Here is what you must do instead
service mysql stop
mv /var/lib/mysql /var/lib/mysql_old
mkdir /var/lib/mysql
chown mysql:mysql /var/lib/mysql
drbdadm primary drbd0
mount /dev/drbd0 /var/lib/mysql
cp -R /var/lib/mysql_old /var/lib/mysql
chown -R mysql:mysql /var/lib/mysql
service mysql start
As shown, stopping mysqld is mandatory.
#UPDATE 2013-03-16 21:46 EDT
There is something incredibly tough you can try
- Given ServerDB1 with MySQL Running
- Given ServerDB2 to introduce as DRBD partner
#STEP 01) Setup DRBD on Separate ServerDB2
As I mentioned earlier, you can house mysql on a DRBD mount.
#STEP 02) Setup MySQL Replication
Huh ??? How did MySQL Replication enter the picture
- You need to mysqldump everything in ServerDB1
- Load the mysqldump into MySQL running in ServerDB2
- Setup Replication so all changes are migrated since loading of ServerDB2 was done
#STEP 03) Failover Your Application
In simple English, use the IP address of ServerDB2 in your application instead of ServerDB1
You should wait and make sure you have a low peak time to do this failover
#STEP 04) Setup DRBD on Separate ServerDB1
- Setup DRBD
- drbdadm secondary drbd0
- drbdadm coonect drbd0
This is an oversimplified description but you can look up the actual code to sync a DRBD pair
Here is my old DRBD download-and-install script
DRBD_VERSION=8.3
DRBD_SUBVERSION=0
DRBD_VERSION_NUMBER=${DRBD_VERSION}.${DRBD_SUBVERSION}
cd
rm -rf drbdinstall
mkdir drbdinstall
cd drbdinstall
wget http://oss.linbit.com/drbd/${DRBD_VERSION}/drbd-${DRBD_VERSION_NUMBER}.tar.gz
gzip -d drbd-${DRBD_VERSION_NUMBER}.tar.gz
tar -xvf drbd-${DRBD_VERSION_NUMBER}.tar
cd drbd-${DRBD_VERSION_NUMBER}
make rpm
rpm -Uvh dist/RPMS/x86_64/drbd-*
You can go to www.drbd.org to find out the latest version number and update the aforemtioned script
Give it a Try !!!