<s>
The	O
Red	O
Hat	O
Cluster	O
includes	O
software	O
to	O
create	O
a	O
high	B-General_Concept
availability	I-General_Concept
and	O
load	B-Application
balancing	I-Application
cluster	O
.	O
</s>
<s>
Both	O
products	O
,	O
the	O
High	B-General_Concept
Availability	I-General_Concept
Add-On	O
and	O
Load	B-Application
Balancer	I-Application
Add-On	O
,	O
are	O
based	O
on	O
open-source	B-License
community	O
projects	O
.	O
</s>
<s>
The	O
High	B-General_Concept
Availability	I-General_Concept
Add-On	O
is	O
Red	O
Hat	O
's	O
implementation	O
of	O
Linux-HA	B-Operating_System
.	O
</s>
<s>
All	O
nodes	O
of	O
the	O
cluster	O
must	O
agree	O
on	O
their	O
configuration	O
and	O
shared	O
services	O
state	O
before	O
the	O
cluster	O
is	O
considered	O
to	O
have	O
a	O
quorum	B-General_Concept
and	O
services	O
are	O
able	O
to	O
be	O
started	O
.	O
</s>
<s>
The	O
primary	O
form	O
of	O
communicating	O
node	O
status	O
is	O
via	O
a	O
network	O
device	O
(	O
commonly	O
Ethernet	O
)	O
,	O
although	O
in	O
the	O
case	O
of	O
possible	O
network	O
failure	O
,	O
quorum	B-General_Concept
can	O
be	O
decided	O
through	O
secondary	O
methods	O
such	O
as	O
shared	O
storage	O
or	O
multicast	O
.	O
</s>
<s>
Software	O
services	O
,	O
filesystems	B-Application
and	O
network	O
status	O
can	O
be	O
monitored	O
and	O
controlled	O
by	O
the	O
cluster	O
suite	O
,	O
services	O
and	O
resources	O
can	O
be	O
failed	O
over	O
to	O
other	O
network	O
nodes	O
in	O
case	O
of	O
failure	O
.	O
</s>
<s>
The	O
node	O
is	O
terminated	O
by	O
removing	O
power	O
(	O
known	O
as	O
STONITH	B-Operating_System
)	O
or	O
access	O
to	O
the	O
shared	O
storage	O
.	O
</s>
<s>
More	O
recent	O
versions	O
of	O
Red	O
Hat	O
use	O
a	O
distributed	B-Operating_System
lock	I-Operating_System
manager	I-Operating_System
,	O
to	O
allow	O
fine	O
grained	O
locking	O
and	O
no	O
single	O
point	O
of	O
failure	O
.	O
</s>
<s>
GULM	O
was	O
last	O
available	O
in	O
Red	B-Operating_System
Hat	I-Operating_System
Cluster	I-Operating_System
Suite	I-Operating_System
4	O
.	O
</s>
<s>
Red	O
Hat	O
adapted	O
the	O
Piranha	O
load	B-Application
balancing	I-Application
software	O
to	O
allow	O
for	O
transparent	O
load	B-Application
balancing	I-Application
and	O
failover	O
between	O
servers	O
.	O
</s>
<s>
The	O
application	O
being	O
balanced	O
does	O
not	O
require	O
special	O
configuration	O
to	O
be	O
balanced	O
,	O
instead	O
a	O
Red	O
Hat	O
Enterprise	O
Linux	O
server	O
with	O
the	O
load	B-Application
balancer	I-Application
configured	O
,	O
intercepts	O
and	O
routes	O
traffic	O
based	O
on	O
metrics/rules	O
set	O
on	O
the	O
load	B-Application
balancer	I-Application
.	O
</s>
<s>
Red	B-Operating_System
Hat	I-Operating_System
cluster	I-Operating_System
suite	I-Operating_System
support	O
is	O
tied	O
to	O
a	O
matching	O
version	O
of	O
Red	O
Hat	O
Enterprise	O
Linux	O
and	O
follows	O
the	O
same	O
maintenance	O
policy	O
.	O
</s>
