8 Install And Configure heartbeat

heartbeat is the control instance of this whole setup. It is going to be installed on server1 and server2, and it monitors the other server. For example, if server1 goes down, heartbeat on server2 detects this and makes server2 take over. heartbeat also starts and stops the NFS server on both server1 and server2. It also provides NFS as a virtual service via the IP address 192.168.0.174 so that the web server cluster nodes see only one NFS server.

First we install heartbeat:

server1/server2:

apt-get install heartbeat

Now we have to create three configuration files for heartbeat. They must be identical on server1 and server2!

server1/server2:

/etc/heartbeat/ha.cf:

logfacility     local0
keepalive 2
#deadtime 30 # USE THIS!!!
deadtime 10
bcast   eth0
node server1 server2

As nodenames we must use the output of uname -n on server1 and server2.

server1/server2:

/etc/heartbeat/haresources:

server1  IPaddr::192.168.0.174/24/eth0 drbddisk::r0 Filesystem::/dev/drbd0::/data::ext3 nfs-kernel-server

The first word is the output of uname -n on server1, no matter if you create the file on server1 or server2! After IPaddr we put our virtual IP address 192.168.0.174, and after drbddisk we use the resource name of our DRBD resource which is r0 here (remember, that is the resource name we use in /etc/drbd.conf - if you use another one, you must use it here, too).

server1/server2:

/etc/heartbeat/authkeys:

auth 3
3 md5 somerandomstring

somerandomstring is a password which the two heartbeat daemons on server1 and server2 use to authenticate against each other. Use your own string here. You have the choice between three authentication mechanisms. I use md5 as it is the most secure one.

/etc/heartbeat/authkeys should be readable by root only, therefore we do this:

server1/server2:

chmod 600 /etc/heartbeat/authkeys

Finally we start DRBD and heartbeat on server1 and server2:

server1/server2:

/etc/init.d/drbd start
/etc/init.d/heartbeat start

9 First Tests

Now we can do our first tests. On server1, run

server1:

ifconfig

In the output, the virtual IP address 192.168.0.174 should show up:

eth0      Link encap:Ethernet  HWaddr 00:0C:29:A1:C5:9B
          inet addr:192.168.0.172  Bcast:192.168.0.255  Mask:255.255.255.0
          inet6 addr: fe80::20c:29ff:fea1:c59b/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:18992 errors:0 dropped:0 overruns:0 frame:0
          TX packets:24816 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:2735887 (2.6 MiB)  TX bytes:28119087 (26.8 MiB)
          Interrupt:177 Base address:0x1400

eth0:0    Link encap:Ethernet  HWaddr 00:0C:29:A1:C5:9B
          inet addr:192.168.0.174  Bcast:192.168.0.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          Interrupt:177 Base address:0x1400

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:71 errors:0 dropped:0 overruns:0 frame:0
          TX packets:71 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:5178 (5.0 KiB)  TX bytes:5178 (5.0 KiB)

Also, run

server1:

df -h

on server1. You should see /data listed there now:

Filesystem            Size  Used Avail Use% Mounted on
/dev/sda5             4.6G  430M  4.0G  10% /
tmpfs                 126M     0  126M   0% /dev/shm
/dev/sda1              89M   11M   74M  13% /boot
/dev/drbd0             24G   33M   23G   1% /data

If you do the same

server2:

ifconfig
df -h

on server2, you shouldn't see 192.168.0.174 and /data.

Now we create a test file in /data/export on server1 and then simulate a server failure of server1 (by stopping heartbeat):

server1:

touch /data/export/test1
/etc/init.d/heartbeat stop

If you run ifconfig and df -h on server2 now, you should see the IP address 192.168.0.174 and the /data partition, and

server2:

ls -l /data/export

should list the file test1 which you created on server1 before. So it has been mirrored to server2!

Now we create another test file on server2 and see if it gets mirrored to server1 when it comes up again:

server2:

touch /data/export/test2

server1:

/etc/init.d/heartbeat start

(Wait a few seconds.)

ifconfig
df -h
ls -l /data/export

You should see 192.168.0.174 and /data again on server1 which means it has taken over again (because we defined it as primary), and you should also see the file /data/export/test2!