<s>
An	O
optical	B-Device
jukebox	I-Device
is	O
a	O
robotic	O
data	B-General_Concept
storage	I-General_Concept
device	I-General_Concept
that	O
can	O
automatically	O
load	O
and	O
unload	O
optical	B-Device
discs	I-Device
,	O
such	O
as	O
Compact	O
Disc	O
,	O
DVD	O
,	O
Ultra	B-Application
Density	I-Application
Optical	I-Application
or	O
Blu-ray	O
and	O
can	O
provide	O
terabytes	O
(	O
TB	O
)	O
or	O
petabytes	O
(	O
PB	O
)	O
of	O
tertiary	O
storage	O
.	O
</s>
<s>
The	O
devices	O
are	O
often	O
called	O
optical	B-Device
disk	I-Device
libraries	I-Device
,	O
"	O
optical	O
storage	O
archives	O
"	O
,	O
robotic	O
drives	O
,	O
or	O
autochangers	O
.	O
</s>
<s>
One	O
of	O
the	O
first	O
examples	O
of	O
an	O
optical	B-Device
jukebox	I-Device
was	O
the	O
unit	O
designed	O
and	O
built	O
at	O
the	O
Royal	O
Aerospace	O
Establishment	O
at	O
Farnborough	O
,	O
England	O
.	O
</s>
<s>
The	O
unit	O
had	O
twin	O
read/write	O
heads	O
,	O
12	O
"	O
WORM	B-Device
disks	O
and	O
the	O
carousels	O
were	O
pneumatically	O
driven	O
.	O
</s>
<s>
Hierarchical	B-Application
storage	I-Application
management	I-Application
is	O
a	O
strategy	O
that	O
moves	O
little-used	O
or	O
unused	O
files	O
from	O
fast	O
magnetic	O
storage	O
to	O
optical	B-Device
jukebox	I-Device
devices	O
in	O
a	O
process	O
called	O
migration	O
.	O
</s>
<s>
Optical	B-Device
disc	I-Device
libraries	O
are	O
also	O
useful	O
for	O
making	O
backups	B-Protocol
and	O
in	O
disaster	B-General_Concept
recovery	I-General_Concept
situations	O
.	O
</s>
<s>
Archiving	O
data	O
is	O
different	O
from	O
backups	B-Protocol
in	O
that	O
the	O
data	O
is	O
stored	O
on	O
media	O
designed	O
to	O
last	O
up	O
to	O
100	O
years	O
.	O
</s>
<s>
The	O
data	O
is	O
usually	O
permanently	O
written	O
on	O
Write	B-Device
Once	I-Device
Read	I-Device
Many	I-Device
(	O
WORM	B-Device
)	O
-type	O
discs	O
so	O
it	O
cannot	O
be	O
erased	O
or	O
changed	O
.	O
</s>
<s>
Jukeboxes	O
typically	O
contain	O
internal	O
SCSI	B-Architecture
-	O
or	O
SATA-based	O
recordable	O
drives	O
(	O
CD-ROM	O
,	O
CD-R	O
,	O
DVD-ROM	O
,	O
DVD-R	O
,	O
DVD-RAM	O
,	O
UDO	O
or	O
Blu-ray	O
)	O
that	O
connect	O
directly	O
to	O
a	O
file	O
server	O
and	O
are	O
managed	O
by	O
a	O
third-party	O
jukebox	O
management	O
software	O
.	O
</s>
<s>
Before	O
the	O
advent	O
of	O
the	O
modern	O
SAN	O
and	O
much	O
cheaper	O
hard	B-Device
disks	I-Device
,	O
high-volume	O
storage	O
on	O
DVD	O
was	O
more	O
cost-effective	O
than	O
magnetic	O
media	O
.	O
</s>
<s>
Optical	B-Device
disc	I-Device
libraries	O
like	O
the	O
TeraStack	O
Solution	O
can	O
store	O
up	O
to	O
142	O
TB	O
of	O
online	O
and	O
nearline	B-General_Concept
data	O
with	O
a	O
nominal	O
power	O
draw	O
of	O
425	O
watts	O
.	O
</s>
<s>
The	O
core	O
functionality	O
of	O
optical	B-Device
library	I-Device
management	O
software	O
can	O
be	O
broken	O
down	O
into	O
four	O
parts	O
:	O
robotic	O
control	O
,	O
filesystem	O
authoring	O
,	O
file	O
tracking	O
,	O
and	O
access	O
control	O
.	O
</s>
<s>
All	O
optical	B-Device
libraries	I-Device
comply	O
with	O
the	O
standard	O
SCSI	B-Architecture
command	O
set	O
.	O
</s>
<s>
When	O
the	O
management	O
software	O
is	O
run	O
,	O
it	O
will	O
send	O
inquiry	O
requests	O
to	O
the	O
optical	B-Device
library	I-Device
for	O
the	O
status	O
of	O
its	O
contents	O
.	O
</s>
<s>
Any	O
of	O
these	O
actions	O
would	O
require	O
specific	O
move	O
commands	O
sent	O
from	O
the	O
management	O
application	O
to	O
the	O
optical	B-Device
library	I-Device
.	O
</s>
<s>
Optical	B-Device
library	I-Device
management	O
software	O
handles	O
all	O
of	O
the	O
writing	O
and	O
reading	O
of	O
the	O
filesystem	O
content	O
on	O
the	O
optical	B-Device
media	I-Device
.	O
</s>
<s>
Filesystem	O
types	O
available	O
for	O
optical	B-Device
media	I-Device
range	O
from	O
ISO	O
standard	O
technologies	O
like	O
UDF	O
to	O
proprietary	O
formats	O
.	O
</s>
<s>
Optical	B-Device
library	I-Device
management	O
software	O
will	O
often	O
track	O
the	O
files	O
and	O
folders	O
extant	O
on	O
a	O
piece	O
of	O
optical	B-Device
media	I-Device
by	O
means	O
of	O
a	O
database	O
.	O
</s>
<s>
Optical	B-Device
library	I-Device
management	O
software	O
makes	O
itself	O
available	O
to	O
the	O
OS	O
in	O
an	O
assortment	O
of	O
ways	O
.	O
</s>
<s>
Essentially	O
,	O
the	O
whole	O
of	O
an	O
optical	B-Device
library	I-Device
can	O
be	O
viewed	O
,	O
read	O
to	O
and	O
written	O
to	O
via	O
a	O
virtual	O
filesystem	O
while	O
the	O
management	O
software	O
handles	O
all	O
of	O
the	O
media	O
movement	O
and	O
I/O	O
requests	O
invisibly	O
in	O
the	O
background	O
.	O
</s>
<s>
Another	O
way	O
that	O
access	O
to	O
the	O
optical	B-Device
library	I-Device
may	O
be	O
accomplished	O
is	O
by	O
way	O
of	O
CIFS	O
shares	O
(	O
more	O
often	O
seen	O
with	O
Unix-type	O
optical	B-Device
library	I-Device
management	O
applications	O
)	O
.	O
</s>
<s>
Here	O
,	O
files	O
accessed	O
are	O
only	O
sent	O
back	O
to	O
the	O
optical	B-Device
discs	I-Device
after	O
they	O
have	O
been	O
utilized	O
.	O
</s>
<s>
Changes	O
may	O
or	O
may	O
not	O
be	O
saved	O
or	O
versioned	O
based	O
on	O
the	O
user	O
configuration	O
and	O
accessibility	O
settings	O
on	O
the	O
storage	O
management	O
software	O
that	O
runs	O
the	O
optical	B-Device
jukebox	I-Device
.	O
</s>
