<s>
Soft	B-Application
updates	I-Application
is	O
an	O
approach	O
to	O
maintaining	O
file	B-Application
system	I-Application
meta-data	O
integrity	O
in	O
the	O
event	O
of	O
a	O
crash	O
or	O
power	O
outage	O
.	O
</s>
<s>
Soft	B-Application
updates	I-Application
work	O
by	O
tracking	O
and	O
enforcing	O
dependencies	O
among	O
updates	O
to	O
file	B-Application
system	I-Application
meta-data	O
.	O
</s>
<s>
Soft	B-Application
updates	I-Application
are	O
an	O
alternative	O
to	O
the	O
more	O
commonly	O
used	O
approach	O
of	O
journaling	B-Application
file	I-Application
systems	I-Application
.	O
</s>
<s>
Soft	B-Application
updates	I-Application
allow	O
only	O
asynchronous	O
metadata	O
writes	O
that	O
do	O
not	O
render	O
the	O
on-disk	O
file	O
system	O
inconsistent	O
,	O
or	O
that	O
the	O
only	O
inconsistency	O
that	O
ever	O
happens	O
is	O
a	O
storage	O
space	O
leak	O
(	O
space	O
marked	O
allocated	O
when	O
not	O
used	O
by	O
any	O
file	O
)	O
.	O
</s>
<s>
Recovery	O
then	O
simply	O
becomes	O
a	O
matter	O
of	O
running	O
a	O
background	O
walk	O
of	O
the	O
file	B-Application
system	I-Application
when	O
it	O
is	O
next	O
mounted	O
to	O
garbage	B-General_Concept
collect	I-General_Concept
any	O
allocated	O
space	O
that	O
has	O
been	O
orphaned	O
.	O
</s>
<s>
This	O
also	O
permits	O
the	O
filesystem	B-Application
to	O
selectively	O
flush	O
certain	O
files	O
without	O
having	O
to	O
flush	O
all	O
metadata	O
blocks	O
or	O
all	O
of	O
the	O
records	O
.	O
</s>
<s>
Soft	B-Application
updates	I-Application
require	O
periodic	O
flushing	O
of	O
the	O
metadata	O
to	O
nonvolatile	O
storage	O
.	O
</s>
<s>
FreeBSD	B-Operating_System
supports	O
soft	B-Application
updates	I-Application
for	O
the	O
UFS	B-Operating_System
file	B-Application
system	I-Application
and	O
they	O
have	O
been	O
enabled	O
by	O
default	O
during	O
installation	O
for	O
many	O
years	O
.	O
</s>
<s>
Soft	B-Application
updates	I-Application
are	O
manually	O
enabled	O
or	O
disabled	O
during	O
file	B-Application
system	I-Application
creation	O
with	O
an	O
option	O
to	O
the	O
newfs	O
command	O
.	O
</s>
<s>
FreeBSD	B-Operating_System
9.0	O
introduced	O
a	O
journaling	O
supplement	O
to	O
soft	B-Application
updates	I-Application
for	O
the	O
purpose	O
of	O
eliminating	O
a	O
background	O
fsck	O
for	O
garbage	B-General_Concept
collection	I-General_Concept
after	O
a	O
crash	O
.	O
</s>
<s>
However	O
,	O
enabling	O
journaling	O
on	O
a	O
filesystem	B-Application
with	O
soft	B-Application
updates	I-Application
disables	O
the	O
ability	O
to	O
make	O
filesystem	B-Application
snapshots	O
.	O
</s>
<s>
This	O
may	O
cause	O
issues	O
when	O
filesystems	B-Application
are	O
dumped	O
with	O
the	O
-L	O
option	O
,	O
as	O
snapshots	O
are	O
used	O
to	O
guarantee	O
filesystem	B-Application
coherency	O
during	O
the	O
dump	O
.	O
</s>
<s>
OpenBSD	B-Operating_System
supports	O
soft	B-Application
updates	I-Application
for	O
the	O
FFS	O
file	B-Application
system	I-Application
.	O
</s>
<s>
Soft	B-Application
updates	I-Application
are	O
enabled	O
when	O
the	O
file	B-Application
system	I-Application
is	O
mounted	O
by	O
exercising	O
an	O
option	O
to	O
the	O
mount	O
command	O
.	O
</s>
<s>
NetBSD	B-Device
supported	O
soft	B-Application
updates	I-Application
until	O
the	O
6.0	O
release	O
(	O
2012	O
)	O
at	O
which	O
time	O
it	O
was	O
deprecated	O
in	O
favor	O
of	O
WAPBL	B-Application
journaling	O
.	O
</s>
<s>
Neither	O
journaling	O
nor	O
soft	B-Application
updates	I-Application
guarantees	O
that	O
no	O
data	O
will	O
be	O
lost	O
,	O
but	O
they	O
do	O
make	O
sure	O
that	O
the	O
filesystem	B-Application
remains	O
consistent	O
.	O
</s>
<s>
An	O
advantage	O
of	O
a	O
file	B-Application
system	I-Application
with	O
soft	B-Application
updates	I-Application
is	O
that	O
it	O
can	O
be	O
mounted	O
immediately	O
after	O
a	O
crash	O
,	O
since	O
there	O
is	O
no	O
log	O
replay	O
.	O
</s>
