<s>
Apple	B-Application
File	I-Application
System	I-Application
(	O
APFS	B-Application
)	O
is	O
a	O
proprietary	B-Application
file	B-Application
system	I-Application
developed	O
and	O
deployed	O
by	O
Apple	O
Inc	O
.	O
for	O
macOS	B-Application
Sierra	O
(	O
10.12.4	O
)	O
and	O
later	O
,	O
iOS	B-Operating_System
10.3	I-Operating_System
and	O
later	O
,	O
tvOS	B-Operating_System
10.2	I-Operating_System
and	O
later	O
,	O
watchOS	B-Device
3.2	I-Device
and	O
later	O
,	O
and	O
all	O
versions	O
of	O
iPadOS	B-Operating_System
.	O
</s>
<s>
It	O
aims	O
to	O
fix	O
core	O
problems	O
of	O
HFS+	B-Application
(	O
also	O
called	O
Mac	B-Application
OS	I-Application
Extended	I-Application
)	O
,	O
APFS	B-Application
's	O
predecessor	O
on	O
these	O
operating	O
systems	O
.	O
</s>
<s>
APFS	B-Application
is	O
optimized	O
for	O
solid-state	B-Device
drive	I-Device
storage	O
and	O
supports	O
encryption	O
,	O
snapshots	B-Application
,	O
and	O
increased	O
data	O
integrity	O
,	O
among	O
other	O
capabilities	O
.	O
</s>
<s>
Apple	B-Application
File	I-Application
System	I-Application
was	O
announced	O
at	O
Apple	O
's	O
developers’	O
conference	O
(	O
WWDC	O
)	O
in	O
June	O
2016	O
as	O
a	O
replacement	O
for	O
HFS+	B-Application
,	O
which	O
had	O
been	O
in	O
use	O
since	O
1998	O
.	O
</s>
<s>
APFS	B-Application
was	O
released	O
for	O
64-bit	B-Device
iOS	B-Application
devices	O
on	O
March	O
27	O
,	O
2017	O
,	O
with	O
the	O
release	O
of	O
iOS	B-Operating_System
10.3	I-Operating_System
,	O
and	O
for	O
macOS	B-Application
devices	O
on	O
September	O
25	O
,	O
2017	O
,	O
with	O
the	O
release	O
of	O
macOS	B-Operating_System
10.13	I-Operating_System
.	O
</s>
<s>
Apple	O
released	O
a	O
partial	O
specification	O
for	O
APFS	B-Application
in	O
September	O
2018	O
which	O
supported	O
read-only	O
access	O
to	O
Apple	B-Application
File	I-Application
Systems	I-Application
on	O
unencrypted	O
,	O
non-Fusion	O
storage	O
devices	O
.	O
</s>
<s>
The	O
file	B-Application
system	I-Application
can	O
be	O
used	O
on	O
devices	O
with	O
relatively	O
small	O
or	O
large	O
amounts	O
of	O
storage	O
.	O
</s>
<s>
It	O
uses	O
64-bit	B-Device
inode	B-Application
numbers	I-Application
,	O
and	O
allows	O
for	O
more	O
secure	O
storage	O
.	O
</s>
<s>
The	O
APFS	B-Application
code	O
,	O
like	O
the	O
HFS+	B-Application
code	O
,	O
uses	O
the	O
TRIM	O
command	O
for	O
better	O
space	O
management	O
and	O
performance	O
.	O
</s>
<s>
It	O
may	O
increase	O
read-write	O
speeds	O
on	O
iOS	B-Application
and	O
macOS	B-Application
,	O
as	O
well	O
as	O
space	O
on	O
iOS	B-Application
devices	O
,	O
due	O
to	O
the	O
way	O
APFS	B-Application
calculates	O
available	O
data	O
.	O
</s>
<s>
APFS	B-Application
uses	O
the	O
GPT	B-Application
partition	I-Application
scheme	O
.	O
</s>
<s>
Within	O
the	O
GPT	B-Application
scheme	O
are	O
one	O
or	O
more	O
APFS	B-Application
containers	O
(	O
partition	O
type	O
GUID	O
is	O
)	O
.	O
</s>
<s>
Within	O
each	O
container	O
there	O
are	O
one	O
or	O
more	O
APFS	B-Application
volumes	B-Application
,	O
all	O
of	O
which	O
share	O
the	O
allocated	O
space	O
of	O
the	O
container	O
,	O
and	O
each	O
volume	O
may	O
have	O
APFS	B-Application
volume	O
roles	O
.	O
</s>
<s>
macOS	B-Device
Catalina	I-Device
(	O
macOS	B-Device
10.15	I-Device
)	O
introduced	O
the	O
APFS	B-Application
volume	O
group	O
,	O
which	O
are	O
groups	O
of	O
volumes	B-Application
that	O
Finder	B-Application
displays	O
as	O
one	O
volume	O
.	O
</s>
<s>
APFS	B-Application
firmlinks	O
lie	O
between	O
hard	B-Application
links	I-Application
and	O
soft	B-Application
links	I-Application
and	O
link	O
between	O
volumes	B-Application
.	O
</s>
<s>
In	O
macOS	B-Device
Catalina	I-Device
the	O
volume	O
role	O
(	O
usually	O
named	O
"	O
Macintosh	O
HD	O
"	O
)	O
became	O
read-only	O
,	O
and	O
in	O
macOS	B-Operating_System
Big	I-Operating_System
Sur	I-Operating_System
(	O
macOS	B-Operating_System
11	I-Operating_System
)	O
it	O
became	O
a	O
signed	O
system	O
volume	O
(	O
SSV	O
)	O
and	O
only	O
volume	O
snapshots	B-Application
are	O
mounted	O
.	O
</s>
<s>
The	O
volume	O
role	O
(	O
usually	O
named	O
"	O
Macintosh	O
HD	O
-	O
Data	O
"	O
)	O
is	O
used	O
as	O
an	O
overlay	O
or	O
shadow	O
of	O
the	O
volume	O
,	O
and	O
both	O
the	O
and	O
volumes	B-Application
are	O
part	O
of	O
the	O
same	O
volume	O
group	O
and	O
shown	O
as	O
one	O
in	O
Finder	B-Application
.	O
</s>
<s>
Changes	O
to	O
a	O
cloned	O
file	O
are	O
saved	O
as	O
delta	B-Algorithm
extents	I-Algorithm
,	O
reducing	O
storage	O
space	O
required	O
for	O
document	O
revisions	O
and	O
copies	O
.	O
</s>
<s>
There	O
is	O
,	O
however	O
,	O
no	O
interface	O
to	O
mark	O
two	O
copies	O
of	O
the	O
same	O
file	O
as	O
clones	O
of	O
the	O
other	O
,	O
or	O
for	O
other	O
types	O
of	O
data	B-General_Concept
deduplication	I-General_Concept
.	O
</s>
<s>
APFS	B-Application
volumes	B-Application
support	O
snapshots	B-Application
for	O
creating	O
a	O
point-in-time	O
,	O
read-only	O
instance	O
of	O
the	O
file	B-Application
system	I-Application
.	O
</s>
<s>
Apple	B-Application
File	I-Application
System	I-Application
natively	O
supports	O
full	O
disk	O
encryption	O
,	O
and	O
file	O
encryption	O
with	O
the	O
following	O
options	O
:	O
</s>
<s>
APFS	B-Application
supports	O
64-bit	B-Device
inode	B-Application
numbers	I-Application
,	O
supporting	O
over	O
9	O
quintillion	O
files	O
(	O
263	O
)	O
on	O
a	O
single	O
volume	O
.	O
</s>
<s>
Apple	B-Application
File	I-Application
System	I-Application
uses	O
checksums	B-Algorithm
to	O
ensure	O
data	O
integrity	O
for	O
metadata	O
.	O
</s>
<s>
Apple	B-Application
File	I-Application
System	I-Application
is	O
designed	O
to	O
avoid	O
metadata	O
corruption	O
caused	O
by	O
system	O
crashes	O
.	O
</s>
<s>
It	O
also	O
avoids	O
having	O
to	O
write	O
the	O
change	O
twice	O
,	O
as	O
happens	O
with	O
an	O
HFS+	B-Application
journaled	O
file	B-Application
system	I-Application
,	O
where	O
changes	O
are	O
written	O
first	O
to	O
the	O
journal	O
and	O
then	O
to	O
the	O
catalog	O
file	O
.	O
</s>
<s>
APFS	B-Application
supports	O
transparent	O
compression	O
on	O
individual	O
files	O
using	O
Deflate	O
(	O
Zlib	O
)	O
,	O
LZVN	B-Application
(	O
libFastCompression	O
)	O
,	O
and	O
LZFSE	B-Application
.	O
</s>
<s>
All	O
three	O
are	O
Lempel-Ziv-type	O
algorithms	O
.	O
</s>
<s>
This	O
feature	O
is	O
inherited	O
from	O
HFS+	B-Application
,	O
and	O
is	O
implemented	O
with	O
the	O
same	O
AppleFSCompression	O
/	O
decmpfs	O
system	O
using	O
resource	O
forks	O
or	O
extended	O
attributes	O
.	O
</s>
<s>
As	O
with	O
HFS+	B-Application
,	O
the	O
transparency	O
is	O
broken	O
for	O
tools	O
that	O
do	O
not	O
use	O
decmpfs-wrapped	O
routines	O
.	O
</s>
<s>
APFS	B-Application
adds	O
the	O
ability	O
to	O
have	O
multiple	O
logical	O
drives	O
(	O
referred	O
to	O
as	O
volumes	B-Application
)	O
in	O
the	O
same	O
container	O
where	O
free	O
space	O
is	O
available	O
to	O
all	O
volumes	B-Application
in	O
that	O
container	O
(	O
block	O
device	O
)	O
.	O
</s>
<s>
While	O
APFS	B-Application
includes	O
numerous	O
improvements	O
relative	O
to	O
its	O
predecessor	O
,	O
HFS+	B-Application
,	O
a	O
number	O
of	O
limitations	O
have	O
been	O
noted	O
.	O
</s>
<s>
APFS	B-Application
does	O
not	O
provide	O
checksums	B-Algorithm
for	O
user	O
data	O
.	O
</s>
<s>
It	O
also	O
does	O
not	O
take	O
advantage	O
of	O
byte-addressable	O
non-volatile	B-General_Concept
random-access	I-General_Concept
memory	I-General_Concept
.	O
</s>
<s>
Enumerating	O
files	O
,	O
and	O
any	O
inode	B-Application
metadata	O
in	O
general	O
,	O
is	O
much	O
slower	O
on	O
APFS	B-Application
when	O
it	O
is	O
located	O
on	O
a	O
hard	B-Device
disk	I-Device
drive	I-Device
.	O
</s>
<s>
This	O
is	O
because	O
instead	O
of	O
storing	O
metadata	O
at	O
a	O
fixed	O
location	O
like	O
HFS+	B-Application
does	O
,	O
APFS	B-Application
stores	O
them	O
alongside	O
the	O
actual	O
file	O
data	O
.	O
</s>
<s>
This	O
fragmentation	O
of	O
metadata	O
means	O
more	O
seeks	O
are	O
performed	O
when	O
listing	O
files	O
,	O
acceptable	O
for	O
SSDs	B-Device
but	O
not	O
HDDs	O
.	O
</s>
<s>
Unlike	O
HFS+	B-Application
,	O
APFS	B-Application
does	O
not	O
support	O
hard	B-Application
links	I-Application
to	O
directories	O
.	O
</s>
<s>
Since	O
the	O
version	O
of	O
the	O
Time	B-Operating_System
Machine	I-Operating_System
backup	O
software	O
included	O
in	O
Mac	B-Application
OS	I-Application
X	O
10.5	O
(	O
Leopard	O
)	O
through	O
macOS	B-Device
10.15	I-Device
(	O
Catalina	O
)	O
relied	O
on	O
hard	B-Application
links	I-Application
to	O
directories	O
,	O
APFS	B-Application
was	O
initially	O
not	O
a	O
supported	O
option	O
for	O
its	O
backup	O
volumes	B-Application
.	O
</s>
<s>
This	O
limitation	O
was	O
overcome	O
starting	O
in	O
macOS	B-Operating_System
11	I-Operating_System
Big	I-Operating_System
Sur	I-Operating_System
,	O
wherein	O
APFS	B-Application
is	O
now	O
the	O
default	O
file	B-Application
system	I-Application
for	O
new	O
Time	B-Operating_System
Machine	I-Operating_System
backups	O
(	O
existing	O
HFS+	B-Application
-formatted	O
backup	O
drives	O
are	O
also	O
still	O
supported	O
)	O
.	O
</s>
<s>
macOS	B-Operating_System
Big	I-Operating_System
Sur	I-Operating_System
's	O
implementation	O
of	O
Time	B-Operating_System
Machine	I-Operating_System
in	O
conjunction	O
with	O
APFS-formatted	O
drives	O
enables	O
"	O
faster	O
,	O
more	O
compact	O
,	O
and	O
more	O
reliable	O
backups	O
"	O
than	O
were	O
possible	O
with	O
HFS+	B-Application
-formatted	O
backup	O
drives	O
.	O
</s>
<s>
In	O
March	O
2018	O
,	O
the	O
APFS	B-Application
driver	O
in	O
High	B-Operating_System
Sierra	I-Operating_System
was	O
found	O
to	O
have	O
a	O
bug	O
that	O
causes	O
the	O
disk	O
encryption	O
password	O
to	O
be	O
logged	O
in	O
plaintext	O
.	O
</s>
<s>
In	O
January	O
2021	O
,	O
the	O
APFS	B-Application
driver	O
in	O
iOS	B-Application
<	O
14.4	O
,	O
macOS	B-Application
<	O
11.2	O
,	O
watchOS	B-Device
<	O
7.3	O
,	O
and	O
tvOS	B-Operating_System
<	O
14.4	O
was	O
found	O
to	O
have	O
a	O
bug	O
that	O
allowed	O
a	O
local	O
user	O
to	O
read	O
arbitrary	O
files	O
,	O
regardless	O
of	O
their	O
permissions	O
.	O
</s>
<s>
An	O
experimental	O
version	O
of	O
APFS	B-Application
,	O
with	O
some	O
limitations	O
,	O
is	O
provided	O
in	O
macOS	B-Operating_System
Sierra	I-Operating_System
10.12.4	O
.	O
</s>
<s>
Among	O
these	O
limitations	O
,	O
it	O
does	O
not	O
perform	O
Unicode	O
normalization	O
while	O
HFS+	B-Application
does	O
,	O
leading	O
to	O
problems	O
with	O
languages	O
other	O
than	O
English	O
.	O
</s>
<s>
Drives	O
formatted	O
with	O
Sierra	O
’s	O
version	O
of	O
APFS	B-Application
may	O
also	O
not	O
be	O
compatible	O
with	O
later	O
versions	O
of	O
macOS	B-Application
or	O
APFS	B-Application
,	O
and	O
the	O
Sierra	O
version	O
of	O
APFS	B-Application
cannot	O
be	O
used	O
with	O
Time	B-Operating_System
Machine	I-Operating_System
,	O
FileVault	O
volumes	B-Application
,	O
or	O
Fusion	B-Device
Drives	I-Device
.	O
</s>
<s>
Since	O
macOS	B-Operating_System
10.13	I-Operating_System
High	I-Operating_System
Sierra	I-Operating_System
,	O
all	O
devices	O
with	O
flash	O
storage	O
are	O
automatically	O
converted	O
to	O
APFS	B-Application
.	O
</s>
<s>
As	O
of	O
macOS	B-Application
10.14	O
Mojave	O
,	O
Fusion	B-Device
Drives	I-Device
and	O
hard	B-Device
disk	I-Device
drives	I-Device
are	O
also	O
upgraded	O
on	O
installation	O
.	O
</s>
<s>
The	O
primary	O
user	O
interface	O
to	O
upgrade	O
does	O
not	O
present	O
an	O
option	O
to	O
opt	O
out	O
of	O
this	O
conversion	O
,	O
and	O
devices	O
formatted	O
with	O
the	O
High	B-Operating_System
Sierra	I-Operating_System
version	O
of	O
APFS	B-Application
will	O
not	O
be	O
readable	O
in	O
previous	O
versions	O
of	O
macOS	B-Application
.	O
</s>
<s>
Users	O
can	O
disable	O
APFS	B-Application
conversion	O
by	O
using	O
the	O
installer	O
's	O
startosinstall	O
utility	O
on	O
the	O
command	O
line	O
and	O
passing	O
--converttoapfs	O
NO	O
.	O
</s>
<s>
FileVault	O
volumes	B-Application
are	O
not	O
converted	O
to	O
APFS	B-Application
as	O
of	O
macOS	B-Operating_System
Big	I-Operating_System
Sur	I-Operating_System
11.2.1	O
.	O
</s>
<s>
Instead	O
macOS	B-Application
formats	O
external	O
FileVault	O
drives	O
as	O
CoreStorage	O
Logical	O
Volumes	B-Application
formatted	O
with	O
Mac	B-Application
OS	I-Application
Extended	I-Application
(	O
Journaled	O
)	O
.	O
</s>
<s>
iOS	B-Operating_System
10.3	I-Operating_System
,	O
tvOS	B-Operating_System
10.2	I-Operating_System
,	O
and	O
watchOS	B-Device
3.2	I-Device
convert	O
the	O
existing	O
HFSX	B-Application
file	B-Application
system	I-Application
to	O
APFS	B-Application
on	O
compatible	O
devices	O
.	O
</s>
<s>
Despite	O
the	O
ubiquity	O
of	O
APFS	B-Application
volumes	B-Application
in	O
today	O
's	O
Macs	O
and	O
the	O
format	O
's	O
2016	O
introduction	O
,	O
third-party	O
repair	O
utilities	O
continue	O
to	O
have	O
notable	O
limitations	O
in	O
supporting	O
APFS	B-Application
volumes	B-Application
,	O
due	O
to	O
Apple	O
's	O
delayed	O
release	O
of	O
complete	O
documentation	O
.	O
</s>
<s>
According	O
to	O
Alsoft	O
,	O
the	O
maker	O
of	O
DiskWarrior	O
,	O
Apple	O
's	O
2018	O
release	O
of	O
partial	O
APFS	B-Application
format	O
documentation	O
has	O
delayed	O
the	O
creation	O
of	O
a	O
version	O
of	O
DiskWarrior	O
that	O
can	O
safely	O
rebuild	O
APFS	B-Application
disks	O
.	O
</s>
<s>
Competing	O
products	O
,	O
including	O
MicroMat	O
's	O
TechTool	O
and	O
Prosoft	O
's	O
Drive	O
Genius	O
,	O
are	O
expected	O
to	O
increase	O
APFS	B-Application
support	O
as	O
well	O
.	O
</s>
<s>
Paragon	O
Software	O
Group	O
has	O
published	O
a	O
software	B-Application
development	I-Application
kit	I-Application
under	O
the	O
4-Clause	O
BSD	B-Operating_System
License	I-Operating_System
that	O
supports	O
read-only	O
access	O
of	O
APFS	B-Application
drives	O
.	O
</s>
<s>
An	O
independent	O
read-only	O
open	B-License
source	I-License
implementation	O
by	O
Joachim	O
Metz	O
,	O
libfsapfs	O
,	O
is	O
released	O
under	O
GNU	B-Application
Lesser	I-Application
General	I-Application
Public	I-Application
License	I-Application
v3	O
.	O
</s>
<s>
It	O
has	O
been	O
packaged	O
into	O
Debian	O
,	O
Fedora	O
Linux	O
,	O
Rocky	O
Linux	O
,	O
Red	O
Hat	O
Enterprise	O
Linux	O
and	O
Ubuntu	B-Operating_System
software	O
repositories	O
.	O
</s>
<s>
Both	O
are	O
command-line	O
tools	O
that	O
do	O
not	O
expose	O
a	O
normal	O
filesystem	B-Application
driver	O
interface	O
.	O
</s>
<s>
There	O
is	O
a	O
Filesystem	B-Application
in	I-Application
Userspace	I-Application
(	O
FUSE	B-Application
)	O
driver	O
for	O
Linux	O
called	O
apfs-fuse	O
with	O
read-only	O
access	O
.	O
</s>
<s>
An	O
"	O
APFS	B-Application
for	O
Linux	O
"	O
project	O
is	O
working	O
to	O
integrate	O
APFS	B-Application
support	O
into	O
the	O
Linux	O
kernel	O
.	O
</s>
