<s>
Pacemaker	B-Operating_System
is	O
an	O
open-source	B-Application
high	O
availability	O
resource	O
manager	O
software	O
used	O
on	O
computer	B-Architecture
clusters	I-Architecture
since	O
2004	O
.	O
</s>
<s>
Until	O
about	O
2007	O
,	O
it	O
was	O
part	O
of	O
the	O
Linux-HA	B-Operating_System
project	O
,	O
then	O
was	O
split	O
out	O
to	O
be	O
its	O
own	O
project	O
.	O
</s>
<s>
Pacemaker	B-Operating_System
is	O
generally	O
used	O
with	O
Corosync	B-Operating_System
Cluster	I-Operating_System
engine	I-Operating_System
or	O
Linux-HA	B-Operating_System
Heartbeat	I-Operating_System
.	O
</s>
