<s>
The	O
Smart	B-Application
File	I-Application
System	I-Application
(	O
SFS	O
)	O
is	O
a	O
journaling	B-Application
filesystem	I-Application
used	O
on	O
Amiga	B-Device
computers	I-Device
and	O
AmigaOS-derived	O
operating	B-General_Concept
systems	I-General_Concept
(	O
though	O
some	O
support	O
also	O
exists	O
for	O
IBM	O
PC	O
compatibles	O
)	O
.	O
</s>
<s>
It	O
is	O
designed	O
for	O
performance	O
,	O
scalability	B-Architecture
and	O
integrity	O
,	O
offering	O
improvements	O
over	O
standard	O
Amiga	B-Device
filesystems	O
as	O
well	O
as	O
some	O
special	O
or	O
unique	O
features	O
.	O
</s>
<s>
SFS	O
uses	O
block	O
sizes	O
ranging	O
from	O
512	O
(	O
29	O
)	O
to	O
32768	O
(	O
215	O
)	O
bytes	B-Application
with	O
a	O
maximum	O
partition	O
size	O
of	O
128	O
GB	O
.	O
</s>
<s>
Its	O
good	O
performance	O
,	O
better	O
than	O
FFS	B-Device
,	O
and	O
lack	O
of	O
need	O
for	O
long	O
"	O
validation	O
"	O
in	O
case	O
of	O
an	O
error	O
,	O
is	O
achieved	O
by	O
grouping	O
multiple	O
directory	O
entries	O
into	O
a	O
single	O
block	O
and	O
by	O
grouping	O
meta	O
data	O
blocks	O
together	O
into	O
clusters	O
.	O
</s>
<s>
A	O
bitmap	B-Application
is	O
used	O
to	O
keep	O
track	O
of	O
free	B-Application
space	O
,	O
and	O
file	O
data	O
is	O
kept	O
track	O
of	O
using	O
extents	O
arranged	O
into	O
a	O
B+	O
tree	O
structure	O
.	O
</s>
<s>
Integrity	O
is	O
maintained	O
by	O
keeping	O
a	O
transaction	B-General_Concept
log	I-General_Concept
of	O
all	O
changes	O
made	O
to	O
metadata	O
over	O
a	O
certain	O
period	O
of	O
time	O
.	O
</s>
<s>
The	O
log	O
is	O
written	O
to	O
disk	O
first	O
into	O
free	B-Application
space	O
and	O
then	O
meta	O
data	O
blocks	O
are	O
overwritten	O
directly	O
.	O
</s>
<s>
Unlike	O
the	O
original	O
Amiga	B-Device
filesystems	O
,	O
FFS	B-Device
and	O
OFS	B-Application
,	O
filesystem	O
integrity	O
is	O
very	O
rarely	O
compromised	O
by	O
this	O
.	O
</s>
<s>
One	O
feature	O
of	O
SFS	O
that	O
is	O
almost	O
unique	O
among	O
Amiga	B-Device
filesystems	O
is	O
its	O
ability	O
to	O
defragment	B-Application
itself	O
while	O
the	O
filesystem	O
is	O
in	O
use	O
,	O
even	O
for	O
locked	O
files	O
.	O
</s>
<s>
The	O
defragmentation	B-Application
process	O
is	O
almost	O
completely	O
stateless	O
(	O
apart	O
from	O
the	O
location	O
it	O
is	O
working	O
on	O
)	O
,	O
which	O
means	O
it	O
can	O
be	O
stopped	O
and	O
started	O
instantly	O
.	O
</s>
<s>
During	O
defragmentation	B-Application
data	O
integrity	O
is	O
ensured	O
of	O
both	O
meta	O
data	O
and	O
normal	O
data	O
.	O
</s>
<s>
SFS	O
is	O
written	O
in	O
C	B-Language
and	O
was	O
originally	O
created	O
and	O
released	O
as	O
freeware	B-License
in	O
1998	O
by	O
John	O
Hendrikx	O
.	O
</s>
<s>
After	O
the	O
original	O
author	O
left	O
the	O
Amiga	B-Device
scene	O
in	O
2000	O
,	O
the	O
source	O
code	O
to	O
SFS	O
was	O
released	O
and	O
its	O
development	O
continued	O
by	O
Ralph	O
Schmidt	O
in	O
MorphOS	B-Operating_System
.	O
</s>
<s>
Since	O
May	O
2005	O
SFSobjec	O
and	O
SFSconfig	O
are	O
available	O
under	O
the	O
GPL	B-License
license	I-License
.	O
</s>
<s>
SFS	O
development	O
has	O
now	O
forked	O
;	O
as	O
well	O
as	O
the	O
original	O
Amiga	B-Device
version	O
,	O
there	O
are	O
now	O
versions	O
for	O
MorphOS	B-Operating_System
,	O
AROS	B-Application
,	O
AmigaOS	B-Application
3	I-Application
,	O
and	O
a	O
version	O
for	O
AmigaOS	B-Application
4	I-Application
,	O
which	O
have	O
different	O
feature	O
sets	O
but	O
remain	O
compatible	O
to	O
each	O
other	O
.	O
</s>
<s>
In	O
addition	O
,	O
there	O
is	O
a	O
driver	O
for	O
Linux	B-Application
to	O
read	O
(	O
experimental	O
to	O
write	O
)	O
Amiga	B-Device
SFS	O
volumes	O
,	O
GRUB	B-Application
natively	O
supports	O
it	O
,	O
and	O
there	O
are	O
free	B-Application
drivers	O
to	O
use	O
it	O
from	O
UEFI	B-Architecture
.	O
</s>
<s>
,	O
SFS	O
was	O
one	O
of	O
the	O
independent	O
filesystems	O
still	O
being	O
used	O
on	O
Amiga	B-Device
computers	I-Device
.	O
</s>
<s>
Versions	O
for	O
AROS	B-Application
,	O
AmigaOS	B-Application
and	O
MorphOS	B-Operating_System
are	O
based	O
on	O
different	O
branches	O
.	O
</s>
<s>
The	O
Linux	B-Application
version	O
is	O
independent	O
code	O
.	O
</s>
