<s>
QNX4FS	B-Application
is	O
an	O
extent-based	O
file	B-Application
system	I-Application
used	O
by	O
the	O
QNX4	B-Operating_System
and	O
QNX6	O
operating	O
systems	O
.	O
</s>
<s>
As	O
the	O
file	B-Application
system	I-Application
uses	O
soft	B-Application
updates	I-Application
,	O
it	O
remains	O
consistent	O
even	O
after	O
a	O
power	O
failure	O
,	O
without	O
using	O
journaling	B-Application
.	O
</s>
<s>
Instead	O
,	O
the	O
writes	O
are	O
carefully	O
ordered	O
and	O
flushed	O
to	O
disk	B-Device
at	O
appropriate	O
intervals	O
so	O
that	O
the	O
on-disk	O
structure	O
always	O
remains	O
consistent	O
,	O
no	O
matter	O
if	O
the	O
operation	O
is	O
interrupted	O
.	O
</s>
<s>
However	O
,	O
unflushed	O
changes	O
to	O
the	O
file	B-Application
system	I-Application
are	O
nevertheless	O
lost	O
,	O
as	O
the	O
disk	B-General_Concept
cache	I-General_Concept
is	O
typically	O
stored	O
in	O
volatile	B-General_Concept
memory	I-General_Concept
.	O
</s>
<s>
This	O
design	O
has	O
a	O
considerable	O
performance	O
gain	O
over	O
journaling	B-Application
,	O
by	O
just	O
bypassing	O
that	O
step	O
.	O
</s>
<s>
Another	O
notable	O
property	O
of	O
this	O
file	B-Application
system	I-Application
is	O
that	O
its	O
actual	O
metadata	O
,	O
like	O
inode	B-Application
information	O
and	O
disk	B-Device
bitmaps	O
,	O
are	O
accessible	O
in	O
the	O
same	O
way	O
as	O
any	O
other	O
file	O
on	O
the	O
file	B-Application
system	I-Application
(	O
as	O
/.inodes	O
and	O
/.bitmap	O
,	O
respectively	O
)	O
.	O
</s>
<s>
This	O
is	O
consistent	O
with	O
QNX	B-Operating_System
's	O
(	O
in	O
fact	O
,	O
Plan	B-Operating_System
9	I-Operating_System
from	I-Operating_System
Bell	I-Operating_System
Labs	I-Operating_System
's	O
,	O
or	O
historically	O
Unix	B-Operating_System
's	O
)	O
philosophy	O
that	O
"	O
everything	B-Application
is	I-Application
a	I-Application
file	I-Application
"	O
.	O
</s>
