====== HA - basics ======
Note: Fibre channel - cheap stuff!!!

**Requirements**
  * Two disks  (preferably same size and my lovely LVM)
  * Networking between machines (node1 & node2), Tip: VMPlayer LAN Segments
  * Working DNS resolution (/etc/hosts file)
  * Selinux disabled
  * Iptables ports (7788) allowed
  * and lot of patience

Install ELRepo repository on your both system:

  rpm -Uvh http://www.elrepo.org/elrepo-release-6-6.el6.elrepo.noarch.rpm

Update both repo:

  yum update -y


Install DRBD:

  [root@node1 ~]# yum -y install drbd84-utils kmod-drbd84
  [root@node2 ~]# yum -y install drbd84-utils kmod-drbd84

Insert drbd module manually on both machines or reboot:

  /sbin/modprobe drbd


====Partition DRBD on both machines (the ugly way):====
If your linux box doesn't detect new disk automaticly, you can try rescanning the scsi bus
   echo "- - -" >/sys/class/scsi_host/host0/scan


  [root@node1 ~]# fdisk -cu /dev/sdb
  [root@node2 ~]# fdisk -cu /dev/sdb
and the right way:
  [root@node1 ~]# lvcreate -L 4GB -n mail_disk vg_jahoda
  [root@node2 ~]# lvcreate -L 4GB -n mail_disk vg_boruvka

==== Setup the network ====
<file bash ifcfg-eth1>
DEVICE="eth1"
BOOTPROTO="none"
HWADDR="00:0C:29:DA:26:E9"
IPADDR="10.1.1.1"
NETMASK="255.255.255.252"
IPV6INIT="yes"
NM_CONTROLLED="no"
ONBOOT="yes"
TYPE="Ethernet"
</file>

==== DRBD config ====
<code bash>
resource mail_disk {
 protocol C;
 startup {
	 wfc-timeout 30;
	 outdated-wfc-timeout 20;
	 degr-wfc-timeout 30;
 }

net {
	 cram-hmac-alg sha1;
	 shared-secret sync_disk;
 }

syncer {
	 rate 100M;
	 al-extents 257;
	 on-no-data-accessible io-error;
 }

on node1 {
	 device /dev/drbd0;
	 disk /dev/jahoda/mail;
	 address 10.1.1.1:7788;
	 flexible-meta-disk internal;
 }

on node2 {
	 device /dev/drbd0;
	 disk /dev/boruvka/mail;
	 address 10.1.1.2:7788;
	 meta-disk internal;
 }
}
</code>

Initialize devices (very similar to pvcreate or mkfs.ext4):
  [root@node1 ~]# drbdadm create-dm mail_disk
  [root@node2 ~]# drbdadm create-dm mail_disk

It is time to start the services. And be careful Jimm, you have 30 seconds to start both.
  [root@node1 ~]# service drbd restart
  [root@node2 ~]# /etc/init.d/drbd restart
  
Check ''cat /proc/drbd'', we should be both Secondary/Secondary and data Inconsistent/Inconsistent. The rest is garbage for geeks.
<code>
version: 8.4.5 (api:1/proto:86-101)
GIT-hash: 1d360bde0e095d495786eaeb2a1ac76888e4db96 build by phil@Build64R6, 2014-10-28 10:32:53
 0: cs:Connected ro:Secondary/Secondary ds:Diskless/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:0
</code>
Careful reader could have notices we are having Diskless/Inconsistent. Initialize (create-dm) the disk again or zero it (dd if=/dev/zero) and initialize again and thing should be fine.

  [root@node1 ~]# drbdadm -- --overwrite-data-of-peer primary mail_disk
  
  
====== UCARP (VRRP) ======
Open the page and install epel
http://mirror.hosting90.cz/epel/6/x86_64/repoview/epel-release.html
Or try using this direct link, but might be unavailable later
   yum install http://mirror.hosting90.cz/epel/6/x86_64/epel-release-6-8.noarch.rpm   

Install ucarp
   yum install ucarp
   
config
<file bash /etc/ucarp.d/vip-001.conf>
  VIP_ADDRESS="192.168.5.123"
</file>

<file bash /etc/ucarp.d/vip-common.conf>
PASSWORD="love"
BIND_INTERFACE="eth0"
SOURCE_ADDRESS="192.168.5.39"


# If you have extra options to add, see "ucarp --help" output
OPTIONS="--shutdown --preempt"
</file>