<s>
The	O
Vsync	O
software	O
library	O
is	O
a	O
BSD-licensed	B-Operating_System
open	O
source	O
library	O
written	O
in	O
C#	B-Application
for	O
the	O
.NET	O
platform	O
,	O
providing	O
a	O
wide	O
variety	O
of	O
primitives	O
for	O
fault-tolerant	B-General_Concept
distributed	B-Architecture
computing	I-Architecture
,	O
including	O
:	O
state	B-Operating_System
machine	I-Operating_System
replication	I-Operating_System
,	O
virtual	O
synchrony	O
process	O
groups	O
,	O
atomic	B-Operating_System
broadcast	I-Operating_System
with	O
several	O
levels	O
of	O
ordering	O
and	O
durability	O
,	O
a	O
distributed	B-Operating_System
lock	I-Operating_System
manager	I-Operating_System
,	O
persistent	O
replicated	B-Architecture
data	I-Architecture
,	O
a	O
distributed	B-Data_Structure
key-value	I-Data_Structure
store	I-Data_Structure
(	O
also	O
called	O
a	O
Distributed	B-Operating_System
Hash	I-Operating_System
Table	I-Operating_System
or	O
DHT	O
)	O
,	O
and	O
scalable	O
aggregation	O
.	O
</s>
<s>
The	O
system	O
implements	O
the	O
virtual	O
synchrony	O
execution	O
model	O
,	O
and	O
includes	O
an	O
implementation	O
of	O
Leslie	O
Lamport	O
's	O
Paxos	B-Operating_System
Protocol	I-Operating_System
.	O
</s>
<s>
Vsync	O
was	O
originally	O
released	O
as	O
Isis2	B-Operating_System
in	O
2010	O
,	O
but	O
Birman	O
changed	O
the	O
name	O
of	O
the	O
package	O
in	O
order	O
to	O
avoid	O
similarity	O
of	O
the	O
name	O
to	O
ISIL	O
.	O
</s>
