Creating a Two Node Mysql Cluster On Ubuntu With DRBD Part 2

This blog is a follow on from a blog post I wrote ages ago and have eventually got round to finishing it off In this part of the process we will create the disks and setup the DRBD devices First we need to connect to the Virtual Machines from a terminal session as it makes life much easier and quicker when you connect remotely. You will need to make sure that your servers have static IP addresses. For this document I will be using the following IP addresses for my servers.

drbdnode1 = 172.16.71.139
drbdnode2 = 172.16.71.140
drbdmstr = 172.16.71.141 (clustered IP address)
Subnet Mask = 255.255.255.0
Gateway = 172.16.71.1
DNS Servers = 8.8.8.8 and 4.4.4.4

So to set the IP address as fixed you need to do the following. Connect to the console of drbdnode1 and login now we need to edit the file that contains the IP address of the network card enter the following command and press return

sudo nano /etc/network/interfaces

enter the password for the user you are logged in as You should see the following screen Edit network now use your arrow keys on your keyboard and move the white cursor to the section that starts with iface eth0 press Ctrl K to remove the line then add the lines below with your IP address details

auto eth0
iface eth0 inet static
address 172.16.71.139
netmask 255.255.255.0
network 172.16.71.0
broadcast 172.16.71.255
gateway 172.16.71.1

It should end up looking like this Edit network complete Now press Ctrl X to exit Then Y Then press Enter to save Now type in the following

sudo /etc/init.d/networking restart

Do the same for drbdnode2 Now that we have given each server a static Ip address we can connect via ssh to the server to do the admin remotely. To do this you need to have a machine that has an ssh client installed most linux and osx clients have one already installed if you are on windows look for putty and use that. So open a terminal on your machine and the in the following

ssh cluster@172.16.71.139 and press enter.

You need to substitute the username you created on your server when setting it up for the word cluster in the above command. You will be prompted to accept a key for the server. Type yes and press enter. Now enter the password for the user and press enter. You should see a screen like this ssh success Connect to both cluster nodes to make sure you are not stopped down the line to fix the problem. You are now ready to work on your cluster. First we need to create host records for the two servers type the following into your terminal session

sudo nano /etc/hosts

and add a record for each server it should look something like this Edit hosts Save the file as before and do the same for node2 but swap the names and ipadresses Now we need to install a few packages that will allow us to use drbd in the terminal on drbdnode1 type

apt-get install heartbeat drbd8-utils

and press enter you should have a screen like this Packages install Press Y and then Enter to install the software. Do this on drbdnode2 as well Now we need to create the partitions that we will use for the drbd cluster to find out which disk we will be using run the command

sudo fdisk -l

to see which disks have not been partitioned your screen should look like this fdisk -l As you can see at the end is the disk /dev/sdb does not have a partition table look for the line “ Disk /dev/sdb doesn't contain a valid partition table “ to create a partition table we need to run the following commands

sudo fdisk /dev/sdb
n (to create a new partition)
p (to select a primary partition)
1 (for the first partition)
Enter (to select the start cylinder)
and enter (to select the end cylinder)
w (to write the changes)

the screen should look like this fdisk -l complete Do this on both servers once this is complete we now need to edit the drbd configuration files to set up our clustered filesystem. In your terminal on drbdnode1 enter the command

sudo nano /etc/drbd.d/clusterdisk.res

Enter the password for your user and edit the file Copy and paste the following code into your terminal screen and then change the details to match your server names and ip addresses

resource clusterdisk {
  # name of resources
  protocol C;
  on drbdnode1 { # first server hostname
  device /dev/drbd0; # Name of DRBD device
  disk /dev/sdb1; # Partition to use, which was created using fdisk
  address 172.16.71.139:7788; # IP addres and port number used by drbd
  meta-disk internal; # where to store metadata meta-data
}

on drbdnode2
{
  # second server hostname
  device /dev/drbd0;
  disk /dev/sdb1;
  address 172.16.71.140:7788;
  meta-disk internal;
}
disk {
  on-io-error detach;
}
net {
  max-buffers 2048;
  ko-count 4;
}
syncer {
  rate 10M;
  al-extents 257;
}
startup {
  wfc-timeout 0;
  degr-wfc-timeout 120; # 2 minutos.
}

}

The screen should look similar to this Edit drbd resource ctrl x (to exit) y (to save the changed file) enter (to overwrite the file) Now we need to create the DRBD resource enter the following command into your terminal session

sudo drbdadm create-md clusterdisk

After running this command you should see a screen similar to this Create DRBD Metadat Disk On drbdnode1 enter the following command

drbdadm -- --overwrite-data-of-peer primary all

this will activate it as the primary drbd node to see if this has worked you can run the following command

sudo drbdadm status

the result should look like this on drbdnode1 Drbdadm status node 1 and like this on drbdnode2 Drbdadm status node2 you will see that drbdnode1 has a status of cs="SyncSource" and drbdnode2 has a status of cs="SyncTarget" this tells you what role they are playing in the cluster at the end of this line you will see a status resynced_percent="3.8" this tells you how much the drbd disk has synced. Once the sync is complete connect to drbdnode1 and run the following command

sudo mkfs.ext4 /dev/drbd0

this will create an ext4 partition on the drbd file system. Which will sync across to drbdnode2

Configuring heartbeat resource

Now we need to setup the Mysql resource in the heartbeat configuration firstly we need to create a file called authkeys. The file should be created in /etc/ha.d directory. You can do this with the following command

nano /etc/ha.d/authkeys

in this file you need to add the following text.

auth 3

3 md5 [SECRETWORD]

Replace [SECRETWORD] with a key you have generated. This file needs to be on both servers in the /etc/ha.d directory. After you have created the file you need to change the permissions on the file to make it more secure. This can be done with the following command

chmod 600 /etc/ha.d/authkeys

do this on both servers Now we need to create the /etc/ha.d/ha.cf file to store the cluster config. You can do this with the following command

nano /etc/ha.d/ha.cf

copy and paste this code into the file

logfile /var/log/ha-log

keepalive 2

deadtime 30

udpport 695

bcast eth0
auto\_failback off
stonith\_host drbdnode1 meatware drbdnode2
stonith\_host drbdnode2 meatware drbdnode1
node drbdnode1 drbdnode2

do the same for both servers next is the haresources file. Create the file here

nano /etc/ha.d/haresources

paste this code in there

dhcp-1 IPaddr::172.16.71.141 /24/eth0 drbddisk::clusterdisk Filesystem::/dev/drbd0::/var/lib/mysql::ext4 mysql

Your cluster is now ready to role. All you now need to do is test the cluster which I will tell you how to do in a future blog post Let me know how you get on