Developers guide

Chapter 8

Operating System Best Practices 69

Make sure you see something like this in /proc/drbd:

...

0: cs:Connected ro:Secondary/Secondary ds:Inconsistent/Inconsistent C r----

ns:0 nr:0 dw:0 dr:0 al:0 bm:0 lo:0 pe:0 ua:0 ap:0 ep:1 wo:b oos:30702640

Synchronize the servers by forcing one to become the primary. So on pf1 do:

# drbdadm -- --overwrite-data-of-peer primary mysql

After issuing this command, the initial full synchronization will start. You will be able to monitor its

progress via /proc/drbd. It may take some time depending on the size of the device. Wait until it

completes.

When the sync is complete, create the filesystem on the primary node only:

# mkfs.ext3 /dev/drbd0

Make sure DRBD is started at boot time:

# chkconfig --level 2345 drbd on

Restart both servers.

When done, look in /proc/drbd and make sure you see:

...

0: cs:Connected ro:Primary/Secondary ds:UpToDate/UpToDate C r---

ns:0 nr:0 dw:0 dr:0 al:0 bm:0 lo:0 pe:0 ua:0 ap:0 ep:1 wo:b oos:0

MySQL Configuration

Note

By default MySQL puts its data in /var/lib/mysql. In order to replicate data between

the two servers, we mount the DRBD partition under /var/lib/mysql.

When first starting MySQL, the partition must be mounted.

In order to do so:

On the master server (the server you are working on), tell DRBD to become the primary node with:

# drbdadm primary mysql

mysql being the name of the DRBD partition.

In /proc/drbd you should see something like: