<s>
Chiron	O
Filesystem	B-Application
is	O
a	O
fault-tolerant	B-General_Concept
replication	O
file	B-Application
system	I-Application
.	O
</s>
<s>
Chiron	B-Application
FS	I-Application
is	O
a	O
FUSE	B-Application
based	O
filesystem	B-Application
that	O
implements	O
replication	O
at	O
the	O
filesystem	B-Application
level	O
like	O
RAID	O
1	O
does	O
at	O
the	O
device	O
level	O
.	O
</s>
<s>
The	O
replicated	O
filesystem	B-Application
may	O
be	O
of	O
any	O
kind	O
;	O
the	O
only	O
requisite	O
is	O
that	O
it	O
is	O
mounted	O
.	O
</s>
<s>
There	O
is	O
no	O
specific	O
communication	O
protocol	O
,	O
at	O
mount	O
time	O
the	O
invoking	O
parameters	O
indicate	O
two	O
or	O
more	O
paths	O
to	O
directories	O
which	O
will	O
be	O
the	O
replicated	O
underlying	O
filesystems	B-Application
(	O
they	O
must	O
be	O
already	O
in	O
sync	O
)	O
.	O
</s>
<s>
This	O
allows	O
the	O
client	O
to	O
use	O
any	O
kind	O
of	O
underlying	O
filesystems	B-Application
such	O
as	O
Ext3	B-Application
,	O
NFS	B-Protocol
or	O
SSHFS	B-Application
and	O
even	O
mix	O
them	O
.	O
</s>
<s>
Every	O
write	O
in	O
the	O
Chiron	B-Application
FS	I-Application
mount	O
point	O
subtree	O
will	O
be	O
echoed	O
to	O
the	O
underlying	O
filesystems	B-Application
.	O
</s>
<s>
Any	O
read	O
from	O
Chiron	B-Application
FS	I-Application
mount	O
point	O
subtree	O
will	O
be	O
made	O
from	O
only	O
one	O
of	O
the	O
underlying	O
filesystems	B-Application
using	O
a	O
prioritized	O
round	O
robin	O
algorithm	O
.	O
</s>
<s>
If	O
one	O
or	O
more	O
underlying	O
filesystems	B-Application
fails	O
,	O
the	O
virtualized	O
filesystem	B-Application
provided	O
by	O
Chiron	B-Application
FS	I-Application
continues	O
operating	O
as	O
long	O
as	O
there	O
is	O
at	O
least	O
one	O
replica	O
available	O
.	O
</s>
<s>
If	O
the	O
failure	O
is	O
on	O
a	O
write	O
operation	O
,	O
the	O
failed	O
replica	O
is	O
disabled	O
and	O
it	O
is	O
not	O
used	O
by	O
Chiron	B-Application
FS	I-Application
until	O
it	O
is	O
available	O
and	O
resynchronized	O
with	O
the	O
others	O
.	O
</s>
<s>
Synchronization	O
is	O
not	O
implemented	O
yet	O
in	O
Chiron	B-Application
FS	I-Application
,	O
so	O
it	O
must	O
be	O
done	O
manually	O
.	O
</s>
<s>
If	O
all	O
replica	O
fails	O
then	O
the	O
calling	O
application	O
receives	O
the	O
error	O
message	O
as	O
it	O
would	O
receive	O
if	O
it	O
was	O
accessing	O
a	O
non	O
replicated	O
filesystem	B-Application
.	O
</s>
