====== Configuring DRBD in a Debian OpenSSI Cluster ======

===== Overview About DRBD =====
  - DRBD is The Distributed Replicated Block Device.

===== 요구사항(Requirements) =====
  - Two computers that are connected to a common switch or hub. 
  - The two computers should also be connected by a Null Modem serial cable \\ to provide the 'heartbeat' system an alternate means of communication. 
  - Each system must independantly have sufficient disk space to provide file service. 

===== 가정(Assumptions) =====
<code>
host-a  10.0.0.10
host-b  10.0.0.20
fs-cluster 10.0.0.30
</code>


===== 과정(Procedure) =====

==== DRBD 모듈설치 ====
  - 양쪽 장비(both hosts) 모두 컴파일하고, 설치한다.<code>
# apt-get install drbd0.7-module-source
# apt-get install drbd0.7-utils
# apt-get install dpatch
# cd /usr/src
# tar -zxf drbd0.7.tar.gz
# cd /usr/src/modules/drbd
# module-assistant prepare
# module-assistant automatic-install drbd0.7-module-source
   Navigate the module package creation procedure as logically as
   possible; details for this procedure are not provided.
# cd /usr/src
# dpkg -i drbd0.7-module-2.4.27-2-k7_0.7.10-3+2.4.27-8_i386.deb
</code>

==== DRBD 구성 ====
  - 양쪽 장비에 /etc/drbd.conf 파일에 동일하게 구성한다. <code>
resource drbd-resource-0 {
  protocol C;
  incon-degr-cmd "halt -f"; # killall heartbeat would be a good alternative :->
  disk {
    on-io-error panic;
  }
  syncer {
    rate 10M; # Note: 'M' is MegaBytes, not MegaBits
  }
  on host-a {
    device    /dev/drbd0;
    disk      /dev/hda8;
    address   10.0.0.10:7789;
    meta-disk  internal;
  }
  on host-b {
    device    /dev/drbd0;
    disk      /dev/hda8;
    address   10.0.0.20:7789;
    meta-disk  internal;
  }
}
</code>
  - 양쪽장비에서 DRBD를 실행한다. <code>
# /etc/init.d/drbd start
</code>
  - 장비 중 하나를 Primary 로 선언한다.<code>
host-a: # drbdadm primary all
</code>
  - DRBD 지정한다.<code>
host-a: # drbdsetup /dev/drbd0 primary --do-what-I-say
</code>
  - Primary 장비에서 DRBD를 위한 파일시스템을 활성화시킨다.<code>
host-a: # mkreiserfs /dev/drbd0  (or mke2fs, or whatever filesystem you
prefer)
host-a: # mkdir /share
host-a: # mkdir /share/spool0
host-a: # mount /dev/drbd0 /share/spool0
</code> 
  - Primary 장비에서 NFS 아래의 공유디렉토리를 생성한다.<code>
host-a: # mkdir /share/spool0/data
</code>
  - 양쪽노드에 NFS 설정을 한다.
    - Debian 패키지를 설치한다.<code>
# apt-get install nfs-kernel-server
</code>
    - NFS 서버를 정지시킨다.<code>
# /etc/init.d/nfs-kernel-server stop
</code>
    - /etc/exports 파일을 설정한다. <code>
# echo "/share/spool0/data 10.3.11.0/255.255.255.0(rw,sync)" >> /etc/exports
</code>
    - 양쪽장비의 NFS 서비스를 자동으로 실행되지 않게 한다.<code>
# update-rc.d -f nfs-kernel-server remove
(for non-Debian systems you can probably just delete /etc/init.d/
nfs or /etc/init.d/nfs-server)
</code>
    - Primary 장비에서 nfs 설정을 공유디스크에 카피하고, 링크시킨다.<code>
host-a: # mv /var/lib/nfs /share/spool0/varlibnfs
host-a: # ln -s /share/spool0/varlibnfs /var/lib/nfs
</code>
    - /etc/default/nfs-common 파일설정을 한다.<code>
# vi /etc/default/nfs-common
...
'STATDOPTS="-n my_clusters_name"
...
</code>

==== heartbeat 설정 ====
  - 패키지를 설치한다.<code>
# apt-get install heartbeat
</code>
  - 양쪽 장비의 /etc/ha.d/ha.cf 를 설정한다. \\ 아래는 Primary 장비의 설정이다. \\ 장비별로 ucast는 다르다. \\ node-b는 10.0.0.20 대신 ucast eth0 10.0.0.10 설정한다. <code>
keepalive 1
deadtime 10
warntime 5
initdead 60
udpport 694
baud 19200
serial /dev/ttyS0
ucast eth0 10.0.0.20
auto_failback off
watchdog /dev/watchdog
node node-a
node node-b
</code>
    * auto_failback is off; we should not fail back unless a human has confirmed that the DRBD state is consistent
  - heartbeat resource 생성한다.<code>
# echo 'killall -9 nfsd ; exit 0' > /etc/heartbeat/resource.d/killnfsd
# chmod 755 /etc/heartbeat/resource.d/killnfsd
</code>
  - /etc/heartbeat/haresources 에 Primary 장비에 설정한다. <code>
host-a  drbddisk::drbd-resource-0 \
        Filesystem::/dev/drbd0::/share/spool0/data::reiserfs \
        killnfsd \
        nfs-common \
        nfs-kernel-server \
        Delay::3::0 \
        IPaddr::10.0.0.30/24/eth0
</code>
  - HA 서버로부터 마운트시킨다.<code>
client-a: # mkdir /mnt/hafs
client-a: # echo "fs-cluster:/share/spool0/data /mnt/hafs nfs defaults 0 0" >> /etc/fstab
client-a: # mount -a
</code>

===== References =====
  - http://www.linux-ha.org/DRBD/NFS