<s>
JBD	B-Application
,	O
or	O
journaling	B-Application
block	I-Application
device	I-Application
,	O
is	O
a	O
generic	O
block	O
device	O
journaling	B-Application
layer	O
in	O
the	O
Linux	B-Operating_System
kernel	I-Operating_System
written	O
by	O
Stephen	O
Tweedie	O
from	O
Red	O
Hat	O
.	O
</s>
<s>
JBD	B-Application
is	O
filesystem-independent	O
.	O
</s>
<s>
ext3	B-Application
,	O
ext4	B-Application
and	O
OCFS2	B-Application
are	O
known	O
to	O
use	O
JBD	B-Application
.	O
</s>
<s>
JBD	B-Application
exists	O
in	O
two	O
versions	O
,	O
JBD	B-Application
and	O
JBD2	B-Application
.	O
</s>
<s>
JBD	B-Application
was	O
created	O
with	O
ext3	B-Application
in	O
1998	O
.	O
</s>
<s>
JBD2	B-Application
was	O
forked	O
from	O
JBD	B-Application
in	O
2006	O
with	O
ext4	B-Application
,	O
with	O
the	O
goal	O
of	O
supporting	O
a	O
64-bit	O
(	O
as	O
opposed	O
to	O
32-bit-only	O
in	O
JBD	B-Application
)	O
block	O
number	O
.	O
</s>
<s>
As	O
a	O
result	O
,	O
the	O
maximum	O
volume	O
size	O
in	O
ext4	B-Application
is	O
increased	O
to	O
1	O
EiB	O
compared	O
to	O
16	O
TiB	O
in	O
ext3	B-Application
(	O
assuming	O
4	O
KiB	O
blocks	O
)	O
.	O
</s>
<s>
JBD2	B-Application
is	O
backward-compatible	O
.	O
</s>
<s>
OCFS2	B-Application
starting	O
from	O
Linux	O
2.6.28	O
uses	O
JBD2	B-Application
.	O
</s>
<s>
The	O
old	O
JBD	B-Application
was	O
removed	O
with	O
the	O
dedicated	O
ext3	B-Application
driver	O
in	O
Linux	B-Operating_System
4.3	O
(	O
2015	O
)	O
.	O
</s>
<s>
For	O
the	O
sake	O
of	O
efficiency	O
and	O
performance	O
,	O
JBD	B-Application
groups	O
several	O
atomic	O
handles	O
into	O
a	O
single	O
transaction	O
,	O
which	O
is	O
written	O
to	O
the	O
journal	O
after	O
a	O
fixed	O
amount	O
of	O
time	O
elapses	O
or	O
there	O
is	O
no	O
free	O
space	O
left	O
on	O
the	O
journal	O
to	O
fit	O
it	O
.	O
</s>
<s>
Based	O
on	O
the	O
transaction	O
states	O
,	O
the	O
JBD	B-Application
is	O
able	O
to	O
determine	O
which	O
transactions	O
need	O
to	O
be	O
replayed	O
(	O
or	O
reapplied	O
)	O
to	O
the	O
file	O
system	O
.	O
</s>
