<s>
In	O
computing	O
,	O
Linux-IO	O
(	O
LIO	B-Application
)	O
Target	O
is	O
an	O
open-source	B-Application
implementation	O
of	O
the	O
SCSI	B-Device
target	I-Device
that	O
has	O
become	O
the	O
standard	O
one	O
included	O
in	O
the	O
Linux	B-Operating_System
kernel	I-Operating_System
.	O
</s>
<s>
Internally	O
,	O
LIO	B-Application
does	O
not	O
initiate	O
sessions	O
,	O
but	O
instead	O
provides	O
one	O
or	O
more	O
Logical	O
Unit	O
Numbers	O
(	O
LUNs	O
)	O
,	O
waits	O
for	O
SCSI	B-Architecture
commands	O
from	O
a	O
SCSI	B-Device
initiator	I-Device
,	O
and	O
performs	O
required	O
input/output	B-General_Concept
data	O
transfers	O
.	O
</s>
<s>
LIO	B-Application
supports	O
common	O
storage	O
fabrics	O
,	O
including	O
FCoE	B-Protocol
,	O
Fibre	B-Architecture
Channel	I-Architecture
,	O
IEEE	B-Protocol
1394	I-Protocol
,	O
iSCSI	B-Protocol
,	O
iSCSI	B-Protocol
Extensions	I-Protocol
for	I-Protocol
RDMA	I-Protocol
(	O
iSER	B-Protocol
)	O
,	O
SCSI	B-Protocol
RDMA	I-Protocol
Protocol	I-Protocol
(	O
SRP	B-Protocol
)	O
and	O
USB	B-Protocol
.	O
</s>
<s>
It	O
is	O
included	O
in	O
most	O
Linux	B-Application
distributions	I-Application
;	O
native	O
support	O
for	O
LIO	B-Application
in	O
QEMU/KVM	O
,	O
libvirt	B-Language
,	O
and	O
OpenStack	B-Application
makes	O
LIO	B-Application
also	O
a	O
storage	O
option	O
for	O
cloud	O
deployments	O
.	O
</s>
<s>
LIO	B-Application
is	O
maintained	O
by	O
Datera	O
,	O
Inc.	O
,	O
a	O
Silicon	O
Valley	O
vendor	O
of	O
storage	B-General_Concept
systems	I-General_Concept
and	O
software	O
.	O
</s>
<s>
On	O
January	O
15	O
,	O
2011	O
,	O
LIO	B-Application
SCSI	B-Device
target	I-Device
engine	O
was	O
merged	O
into	O
the	O
Linux	B-Operating_System
kernel	I-Operating_System
mainline	O
,	O
in	O
kernel	B-Operating_System
version	O
2.6.38	O
,	O
which	O
was	O
released	O
on	O
March	O
14	O
,	O
2011	O
.	O
</s>
<s>
Additional	O
fabric	O
modules	O
have	O
been	O
merged	O
into	O
subsequent	O
Linux	B-Application
releases	O
.	O
</s>
<s>
A	O
competing	O
generic	O
SCSI	B-Device
target	I-Device
module	O
for	O
Linux	B-Application
is	O
SCST	B-Application
.	O
</s>
<s>
For	O
the	O
narrower	O
purpose	O
providing	O
a	O
Linux	B-Application
iSCSI	B-Protocol
target	O
,	O
the	O
older	O
IET	O
(	O
"	O
iSCSI	B-Protocol
Enterprise	O
Target	O
"	O
)	O
and	O
STGT	O
(	O
"	O
SCSI	B-Device
Target	I-Device
Framework	O
"	O
)	O
modules	O
also	O
enjoy	O
industry	O
support	O
.	O
</s>
<s>
The	O
SCSI	B-Architecture
standard	O
provides	O
an	O
extensible	O
semantic	O
abstraction	O
for	O
computer	B-General_Concept
data	I-General_Concept
storage	I-General_Concept
devices	O
,	O
and	O
as	O
such	O
has	O
become	O
a	O
"	O
lingua	O
franca	O
"	O
for	O
data	O
storage	B-General_Concept
systems	I-General_Concept
.	O
</s>
<s>
The	O
SCSI	B-Architecture
T10	O
standards	O
define	O
the	O
commands	O
and	O
protocols	O
of	O
the	O
SCSI	B-Architecture
command	O
processor	O
(	O
sent	O
in	O
SCSI	B-Architecture
CDBs	O
)	O
,	O
and	O
the	O
electrical	O
and	O
optical	O
interfaces	O
for	O
various	O
implementations	O
.	O
</s>
<s>
A	O
SCSI	B-Device
initiator	I-Device
is	O
an	O
endpoint	O
that	O
initiates	O
a	O
SCSI	B-Architecture
session	O
.	O
</s>
<s>
A	O
SCSI	B-Device
target	I-Device
is	O
the	O
endpoint	O
that	O
waits	O
for	O
initiator	O
commands	O
and	O
executes	O
the	O
required	O
I/O	B-General_Concept
data	O
transfers	O
.	O
</s>
<s>
The	O
SCSI	B-Device
target	I-Device
usually	O
exports	O
one	O
or	O
more	O
LUNs	O
for	O
initiators	O
to	O
operate	O
on	O
.	O
</s>
<s>
The	O
LIO	B-Application
Linux	B-Application
SCSI	B-Device
Target	I-Device
implements	O
a	O
generic	O
SCSI	B-Device
target	I-Device
that	O
provides	O
remote	O
access	O
to	O
most	O
data	O
storage	O
device	O
types	O
over	O
all	O
prevalent	O
storage	O
fabrics	O
and	O
protocols	O
.	O
</s>
<s>
LIO	B-Application
neither	O
directly	O
accesses	O
data	O
nor	O
does	O
it	O
directly	O
communicate	O
with	O
applications	O
.	O
</s>
<s>
LIO	B-Application
provides	O
a	O
highly	O
efficient	O
,	O
fabric-independent	O
and	O
fabric-transparent	O
abstraction	O
for	O
the	O
semantics	O
of	O
numerous	O
data	O
storage	O
device	O
types	O
.	O
</s>
<s>
LIO	B-Application
implements	O
a	O
modular	O
and	O
extensible	O
architecture	O
around	O
a	O
versatile	O
and	O
highly	O
efficient	O
,	O
parallelized	O
SCSI	B-Architecture
command	O
processing	O
engine	O
.	O
</s>
<s>
The	O
SCSI	B-Device
target	I-Device
engine	O
implements	O
the	O
semantics	O
of	O
a	O
SCSI	B-Device
target	I-Device
.	O
</s>
<s>
The	O
LIO	B-Application
SCSI	B-Device
target	I-Device
engine	O
is	O
independent	O
of	O
specific	O
fabric	O
modules	O
or	O
backstore	O
types	O
.	O
</s>
<s>
Thus	O
,	O
LIO	B-Application
supports	O
mixing	O
and	O
matching	O
any	O
number	O
of	O
fabrics	O
and	O
backstores	O
at	O
the	O
same	O
time	O
.	O
</s>
<s>
The	O
LIO	B-Application
SCSI	B-Device
target	I-Device
engine	O
implements	O
a	O
comprehensive	O
SPC-3/SPC	O
-4	O
feature	O
set	O
with	O
support	O
for	O
high-end	O
features	O
,	O
including	O
SCSI-3/SCSI	O
-4	O
Persistent	O
Reservations	O
(	O
PRs	O
)	O
,	O
SCSI-4	O
Asymmetric	O
Logical	O
Unit	O
Assignment	O
(	O
ALUA	O
)	O
,	O
VMware	O
vSphere	O
APIs	O
for	O
Array	O
Integration	O
(	O
VAAI	O
)	O
,	O
T10	B-Error_Name
DIF	I-Error_Name
,	O
etc	O
.	O
</s>
<s>
LIO	B-Application
is	O
configurable	O
via	O
a	O
configfs-based	O
kernel	B-Operating_System
API	O
,	O
and	O
can	O
be	O
managed	O
via	O
a	O
command-line	B-Application
interface	I-Application
and	O
API	O
(	O
targetcli	O
)	O
.	O
</s>
<s>
The	O
concept	O
of	O
a	O
SCSI	B-Device
target	I-Device
is	O
n't	O
narrowly	O
restricted	O
to	O
physical	B-Device
devices	I-Device
on	O
a	O
SCSI	B-Architecture
bus	O
,	O
but	O
instead	O
provides	O
a	O
generalized	O
model	O
for	O
all	O
receivers	O
on	O
a	O
logical	O
SCSI	B-Architecture
fabric	O
.	O
</s>
<s>
This	O
includes	O
SCSI	B-Architecture
sessions	O
across	O
interconnects	O
with	O
no	O
physical	O
SCSI	B-Architecture
bus	O
at	O
all	O
.	O
</s>
<s>
Conceptually	O
,	O
the	O
SCSI	B-Device
target	I-Device
provides	O
a	O
generic	O
block	O
storage	O
service	O
or	O
server	B-Application
in	O
this	O
scenario	O
.	O
</s>
<s>
Backstores	O
provide	O
the	O
SCSI	B-Device
target	I-Device
with	O
generalized	O
access	O
to	O
data	O
storage	O
devices	O
by	O
importing	O
them	O
via	O
corresponding	O
device	O
drivers	O
.	O
</s>
<s>
Backstores	O
do	O
n't	O
need	O
to	O
be	O
physical	O
SCSI	B-Architecture
devices	O
.	O
</s>
<s>
Block	O
:	O
The	O
block	O
driver	O
allows	O
using	O
raw	O
Linux	B-Application
block	O
devices	O
as	O
backstores	O
for	O
export	O
via	O
LIO	B-Application
.	O
</s>
<s>
This	O
includes	O
physical	B-Device
devices	I-Device
,	O
such	O
as	O
HDDs	O
,	O
SSDs	B-Device
,	O
CDs/DVDs	O
,	O
RAM	B-Application
disks	I-Application
,	O
etc.	O
,	O
and	O
logical	O
devices	O
,	O
such	O
as	O
software	O
or	O
hardware	O
RAID	B-Architecture
volumes	O
or	O
LVM	B-Application
volumes	O
.	O
</s>
<s>
File	O
:	O
The	O
file	O
driver	O
allows	O
using	O
files	O
that	O
can	O
reside	O
in	O
any	O
Linux	B-Application
file	B-Application
system	I-Application
or	O
clustered	B-Application
file	I-Application
system	I-Application
as	O
backstores	O
for	O
export	O
via	O
LIO	B-Application
.	O
</s>
<s>
Raw	O
:	O
The	O
raw	O
driver	O
allows	O
using	O
unstructured	O
memory	O
as	O
backstores	O
for	O
export	O
via	O
LIO	B-Application
.	O
</s>
<s>
As	O
a	O
result	O
,	O
LIO	B-Application
provides	O
a	O
generalized	O
model	O
to	O
export	O
block	O
storage	O
.	O
</s>
<s>
Fabric	O
modules	O
implement	O
the	O
frontend	O
of	O
the	O
SCSI	B-Device
target	I-Device
by	O
encapsulating	O
and	O
abstracting	O
the	O
properties	O
of	O
the	O
various	O
supported	O
interconnect	O
.	O
</s>
<s>
The	O
Fibre	B-Protocol
Channel	I-Protocol
over	I-Protocol
Ethernet	I-Protocol
(	O
FCoE	B-Protocol
)	O
fabric	O
module	O
allows	O
the	O
transport	O
of	O
Fibre	B-Architecture
Channel	I-Architecture
protocol	O
(	O
FCP	O
)	O
traffic	O
across	O
lossless	B-Protocol
Ethernet	I-Protocol
networks	O
.	O
</s>
<s>
The	O
specification	O
,	O
supported	O
by	O
a	O
large	O
number	O
of	O
network	O
and	O
storage	O
vendors	O
,	O
is	O
part	O
of	O
the	O
Technical	O
Committee	O
T11	O
FC-BB-5	O
standard	O
.	O
</s>
<s>
LIO	B-Application
supports	O
all	O
standard	O
Ethernet	O
NICs	O
.	O
</s>
<s>
The	O
FCoE	B-Protocol
fabric	O
module	O
was	O
contributed	O
by	O
Cisco	O
and	O
Intel	O
,	O
and	O
released	O
with	O
Linux	B-Application
3.0	O
on	O
July	O
21	O
,	O
2011	O
.	O
</s>
<s>
Fibre	B-Architecture
Channel	I-Architecture
is	O
a	O
high-speed	O
network	O
technology	O
primarily	O
used	O
for	O
storage	O
networking	O
.	O
</s>
<s>
The	O
QLogic	O
Fibre	B-Architecture
Channel	I-Architecture
fabric	O
module	O
supports	O
4	O
-	O
and	O
8-gigabit	O
speeds	O
with	O
the	O
following	O
HBAs	O
:	O
</s>
<s>
The	O
Fibre	B-Architecture
Channel	I-Architecture
fabric	O
module	O
and	O
low-level	O
driver	O
(	O
LLD	O
)	O
were	O
released	O
with	O
Linux	B-Application
3.5	O
on	O
July	O
21	O
,	O
2012	O
.	O
</s>
<s>
With	O
Linux	B-Application
3.9	O
,	O
the	O
following	O
QLogic	O
HBAs	O
and	O
CNAs	O
are	O
also	O
supported	O
:	O
</s>
<s>
This	O
makes	O
LIO	B-Application
the	O
first	O
open	O
source	O
target	O
to	O
support	O
16-gigabit	O
Fibre	B-Architecture
Channel	I-Architecture
.	O
</s>
<s>
The	O
FireWire	B-Protocol
SBP-2	O
fabric	O
module	O
enables	O
Linux	B-Application
to	O
export	O
local	O
storage	O
devices	O
via	O
IEEE	B-Protocol
1394	I-Protocol
,	O
so	O
that	O
other	O
systems	O
can	O
mount	O
them	O
as	O
an	O
ordinary	O
IEEE	B-Protocol
1394	I-Protocol
storage	O
device	O
.	O
</s>
<s>
IEEE	B-Protocol
1394	I-Protocol
is	O
a	O
serial	O
bus	O
interface	O
standard	O
for	O
high-speed	O
communications	O
and	O
isochronous	O
real-time	O
data	O
transfer	O
.	O
</s>
<s>
It	O
was	O
developed	O
by	O
Apple	O
as	O
"	O
FireWire	B-Protocol
"	O
in	O
the	O
late	O
1980	O
's	O
and	O
early	O
1990	O
's	O
,	O
and	O
Macintosh	B-Device
computers	O
have	O
supported	O
"	O
FireWire	B-Protocol
target	O
disk	O
mode	O
"	O
since	O
1999	O
.	O
</s>
<s>
The	O
FireWire	B-Protocol
SBP-2	O
fabric	O
module	O
was	O
released	O
with	O
Linux	B-Application
3.5	O
on	O
July	O
21	O
,	O
2012	O
.	O
</s>
<s>
The	O
Internet	O
Small	B-Architecture
Computer	I-Architecture
System	I-Architecture
Interface	I-Architecture
(	O
iSCSI	B-Protocol
)	O
fabric	O
module	O
allows	O
the	O
transport	O
of	O
SCSI	B-Architecture
traffic	O
across	O
standard	O
IP	O
networks	O
.	O
</s>
<s>
By	O
carrying	O
SCSI	B-Architecture
sessions	O
across	O
IP	O
networks	O
,	O
iSCSI	B-Protocol
is	O
used	O
to	O
facilitate	O
data	O
transfers	O
over	O
intranets	O
and	O
to	O
manage	O
storage	O
over	O
long	O
distances	O
.	O
</s>
<s>
iSCSI	B-Protocol
can	O
be	O
used	O
to	O
transmit	O
data	O
over	O
local	O
area	O
networks	O
(	O
LANs	O
)	O
,	O
wide	O
area	O
networks	O
(	O
WANs	O
)	O
,	O
or	O
the	O
Internet	O
,	O
and	O
can	O
enable	O
location-independent	O
and	O
location-transparent	O
data	O
storage	O
and	O
retrieval	O
.	O
</s>
<s>
The	O
LIO	B-Application
iSCSI	B-Protocol
fabric	O
module	O
also	O
implements	O
a	O
number	O
of	O
advanced	O
iSCSI	B-Protocol
features	O
that	O
increase	O
performance	O
and	O
resiliency	O
,	O
such	O
as	O
Multiple	O
Connections	O
per	O
Session	O
(	O
MC/S	O
)	O
and	O
Error	O
Recovery	O
Levels	O
0-2	O
(	O
ERL	O
=	O
0	O
,	O
1	O
,	O
2	O
)	O
.	O
</s>
<s>
LIO	B-Application
supports	O
all	O
standard	O
Ethernet	O
NICs	O
.	O
</s>
<s>
The	O
iSCSI	B-Protocol
fabric	O
module	O
was	O
released	O
with	O
Linux	B-Application
3.1	O
on	O
October	O
24	O
,	O
2011	O
.	O
</s>
<s>
Networks	O
supporting	O
remote	B-General_Concept
direct	I-General_Concept
memory	I-General_Concept
access	I-General_Concept
(	O
RDMA	B-General_Concept
)	O
can	O
use	O
the	O
iSCSI	B-Protocol
Extensions	I-Protocol
for	I-Protocol
RDMA	I-Protocol
(	O
iSER	B-Protocol
)	O
fabric	O
module	O
to	O
transport	O
iSCSI	B-Protocol
traffic	O
.	O
</s>
<s>
iSER	B-Protocol
permits	O
data	O
to	O
be	O
transferred	O
directly	O
into	O
and	O
out	O
of	O
remote	O
SCSI	B-Architecture
computer	O
memory	O
buffers	O
without	O
intermediate	O
data	O
copies	O
(	O
direct	O
data	O
placement	O
or	O
DDP	O
)	O
by	O
using	O
RDMA	B-General_Concept
.	O
</s>
<s>
RDMA	B-General_Concept
is	O
supported	O
on	O
InfiniBand	B-Architecture
networks	O
,	O
on	O
Ethernet	O
with	O
data	B-Protocol
center	I-Protocol
bridging	I-Protocol
(	O
DCB	O
)	O
networks	O
via	O
RDMA	B-Operating_System
over	I-Operating_System
Converged	I-Operating_System
Ethernet	I-Operating_System
(	O
RoCE	O
)	O
,	O
and	O
on	O
standard	O
Ethernet	O
networks	O
with	O
iWARP	B-Device
enhanced	O
TCP	B-Protocol
offload	I-Protocol
engine	I-Protocol
controllers	O
.	O
</s>
<s>
The	O
iSER	B-Protocol
fabric	O
module	O
was	O
developed	O
together	O
by	O
Datera	O
and	O
Mellanox	O
Technologies	O
,	O
and	O
first	O
released	O
with	O
Linux	B-Application
3.10	O
on	O
June	O
30	O
,	O
2013	O
.	O
</s>
<s>
The	O
SCSI	B-Protocol
RDMA	I-Protocol
Protocol	I-Protocol
(	O
SRP	B-Protocol
)	O
fabric	O
module	O
allows	O
the	O
transport	O
of	O
SCSI	B-Architecture
traffic	O
across	O
RDMA	B-General_Concept
(	O
see	O
above	O
)	O
networks	O
.	O
</s>
<s>
As	O
of	O
2013	O
,	O
SRP	B-Protocol
was	O
more	O
widely	O
used	O
than	O
iSER	B-Protocol
,	O
although	O
it	O
is	O
more	O
limited	O
,	O
as	O
SCSI	B-Architecture
is	O
only	O
a	O
peer-to-peer	O
protocol	O
,	O
whereas	O
iSCSI	B-Protocol
is	O
fully	O
routable	O
.	O
</s>
<s>
The	O
SRP	B-Protocol
fabric	O
module	O
supports	O
the	O
following	O
Mellanox	O
host	B-Architecture
channel	I-Architecture
adapters	I-Architecture
(	O
HCAs	O
)	O
:	O
</s>
<s>
The	O
SRP	B-Protocol
fabric	O
module	O
was	O
released	O
with	O
Linux	B-Application
3.3	O
on	O
March	O
18	O
,	O
2012	O
.	O
</s>
<s>
In	O
2012	O
,	O
c't	O
magazine	O
measured	O
almost	O
5000	O
MB/s	O
throughput	O
with	O
LIO	B-Application
SRP	B-Protocol
Target	O
over	O
one	O
Mellanox	O
ConnectX-3	O
port	O
in	O
56	O
Gbit/s	O
FDR	O
mode	O
on	O
a	O
Sandy	B-Device
Bridge	I-Device
PCI	O
Express	O
3.0	O
system	O
with	O
four	O
Fusion-IO	O
ioDrive	O
PCI	O
Express	O
flash	O
memory	O
cards	O
.	O
</s>
<s>
The	O
USB	B-Protocol
Gadget	O
fabric	O
module	O
enables	O
Linux	B-Application
to	O
export	O
local	O
storage	O
devices	O
via	O
the	O
Universal	B-Protocol
Serial	I-Protocol
Bus	I-Protocol
(	O
USB	B-Protocol
)	O
,	O
so	O
that	O
other	O
systems	O
can	O
mount	O
them	O
as	O
an	O
ordinary	O
storage	O
device	O
.	O
</s>
<s>
USB	B-Protocol
was	O
designed	O
in	O
the	O
mid-1990s	O
to	O
standardize	O
the	O
connection	O
of	O
computer	B-Device
peripherals	I-Device
,	O
and	O
has	O
also	O
become	O
common	O
for	O
data	O
storage	O
devices	O
.	O
</s>
<s>
The	O
USB	B-Protocol
Gadget	O
fabric	O
module	O
was	O
released	O
with	O
Linux	B-Application
3.5	O
on	O
July	O
21	O
,	O
2012	O
.	O
</s>
<s>
targetcli	O
is	O
a	O
user	O
space	O
single-node	O
management	O
command	B-Application
line	I-Application
interface	I-Application
(	O
CLI	O
)	O
for	O
LIO	B-Application
.	O
</s>
<s>
targetcli	O
is	O
implemented	O
in	O
Python	B-Language
and	O
consists	O
of	O
three	O
main	O
modules	O
:	O
</s>
<s>
Detailed	O
instructions	O
on	O
how	O
to	O
set	O
up	O
LIO	B-Application
targets	I-Application
can	O
be	O
found	O
on	O
the	O
LIO	B-Application
wiki	O
.	O
</s>
<s>
targetcli	O
and	O
LIO	B-Application
are	O
included	O
in	O
most	O
Linux	B-Application
distributions	I-Application
per	O
default	O
.	O
</s>
<s>
Distribution	O
Version	O
Release	O
Archive	O
Installation	O
Source	O
git	O
Documentation	O
Alpine	O
Linux	B-Application
2.5	O
2011-11-07	O
Alpine	O
Linux	B-Application
mirror	O
apk	O
add	O
targetcli-fb	O
targetcli-fb.git	O
How-to	O
CentOS	O
6.2	O
2011-12-20	O
CentOS	O
mirror	O
su	O
-c	O
'	O
yum	O
install	O
fcoe-target-utils	O
'	O
targetcli-fb.git	O
Tech	O
Notes	O
Debian	O
7.0	O
(	O
"	O
wheezy	O
"	O
)	O
2013-05-04	O
Debian	O
pool	O
su	O
-c	O
'	O
apt-get	O
install	O
targetcli	O
 '	O
targetcli.git	O
LIO	B-Application
Wiki	O
Fedora	O
16	O
2011-11-08	O
Fedora	O
Rawhide	O
su	O
-c	O
'	O
yum	O
install	O
targetcli	O
 '	O
targetcli-fb.git	O
Target	O
Wiki	O
openSUSE	B-Operating_System
12.1	O
2011-11-08	O
Requires	O
manual	O
installation	O
from	O
Datera	O
targetcli.git	O
repos	O
.	O
</s>
