<s>
In	O
computing	O
,	O
thin	B-General_Concept
provisioning	I-General_Concept
involves	O
using	O
virtualization	B-General_Concept
technology	I-General_Concept
to	O
give	O
the	O
appearance	O
of	O
having	O
more	O
physical	O
resources	O
than	O
are	O
actually	O
available	O
.	O
</s>
<s>
The	O
term	O
thin	B-General_Concept
provisioning	I-General_Concept
is	O
applied	O
to	O
disk	O
layer	O
in	O
this	O
article	O
,	O
but	O
could	O
refer	O
to	O
an	O
allocation	O
scheme	O
for	O
any	O
resource	O
.	O
</s>
<s>
The	O
efficiency	O
of	O
thin	O
or	O
thick/fat	O
provisioning	O
is	O
a	O
function	O
of	O
the	O
use	B-Architecture
case	I-Architecture
,	O
not	O
of	O
the	O
technology	O
.	O
</s>
<s>
Thin	B-General_Concept
provisioning	I-General_Concept
offers	O
more	O
efficiency	O
where	O
the	O
amount	O
of	O
resource	O
used	O
is	O
much	O
smaller	O
than	O
allocated	O
,	O
so	O
that	O
the	O
benefit	O
of	O
providing	O
only	O
the	O
resource	O
needed	O
exceeds	O
the	O
cost	O
of	O
the	O
virtualization	B-General_Concept
technology	I-General_Concept
used	O
.	O
</s>
<s>
Just-in-time	O
allocation	O
differs	O
from	O
thin	B-General_Concept
provisioning	I-General_Concept
.	O
</s>
<s>
Overallocation	O
also	O
differs	O
from	O
thin	B-General_Concept
provisioning	I-General_Concept
;	O
resources	O
can	O
be	O
over-allocated	O
/	O
oversubscribed	O
without	O
using	O
virtualization	B-General_Concept
technology	I-General_Concept
,	O
for	O
example	O
overselling	O
seats	O
on	O
a	O
flight	O
without	O
allocating	O
actual	O
seats	O
at	O
time	O
of	O
sale	O
,	O
avoiding	O
having	O
each	O
consumer	O
having	O
a	O
claim	O
on	O
a	O
specific	O
seat	O
number	O
.	O
</s>
<s>
Thin	B-General_Concept
provisioning	I-General_Concept
is	O
a	O
mechanism	O
that	O
applies	O
to	O
large-scale	O
centralized	O
computer	O
disk-storage	O
systems	O
,	O
SANs	O
,	O
and	O
storage	B-Application
virtualization	I-Application
systems	O
.	O
</s>
<s>
Thin	B-General_Concept
provisioning	I-General_Concept
allows	O
space	O
to	O
be	O
easily	O
allocated	O
to	O
servers	O
,	O
on	O
a	O
just-enough	O
and	O
just-in-time	O
basis	O
.	O
</s>
<s>
Thin	B-General_Concept
provisioning	I-General_Concept
is	O
called	O
"	O
sparse	O
volumes	O
"	O
in	O
some	O
contexts	O
.	O
</s>
<s>
Thin	B-General_Concept
provisioning	I-General_Concept
,	O
in	O
a	O
shared-storage	O
environment	O
,	O
provides	O
a	O
method	O
for	O
optimizing	O
utilization	O
of	O
available	O
storage	O
.	O
</s>
<s>
With	O
thin	B-General_Concept
provisioning	I-General_Concept
,	O
storage	O
capacity	O
utilization	O
efficiency	O
can	O
be	O
automatically	O
driven	O
up	O
towards	O
100%	O
with	O
very	O
little	O
administrative	O
overhead	O
.	O
</s>
<s>
Thin	O
technology	O
on	O
a	O
storage	B-Application
virtualization	I-Application
frame	O
was	O
first	O
introduced	O
by	O
VMware	O
as	O
part	O
of	O
their	O
VMware	B-Operating_System
Workstation	I-Operating_System
and	O
VMware	B-Operating_System
ESX	I-Operating_System
products	O
in	O
early	O
2001	O
.	O
</s>
<s>
Thin	B-General_Concept
provisioning	I-General_Concept
enables	O
over-allocation	O
or	O
over-subscription	O
.	O
</s>
<s>
Over-allocation	O
or	O
over-subscription	O
is	O
a	O
mechanism	O
that	O
allows	O
a	O
server	B-Application
to	O
view	O
more	O
storage	O
capacity	O
than	O
has	O
been	O
physically	O
reserved	O
on	O
the	O
storage	O
array	O
itself	O
.	O
</s>
<s>
As	O
a	O
practical	O
consideration	O
,	O
a	O
storage	O
manager	O
needs	O
to	O
monitor	O
actual	O
storage	O
used	O
,	O
adding	O
additional	O
storage	O
capacity	O
such	O
as	O
disks	O
,	O
tapes	O
,	O
solid-state	B-Device
drives	I-Device
(	O
SSD	B-Device
)	O
,	O
etc	O
.	O
</s>
<s>
as	O
necessary	O
to	O
satisfy	O
the	O
write	O
requests	O
of	O
the	O
server	B-Application
and	O
residing	O
application(s )	O
.	O
</s>
<s>
The	O
over-allocation	O
concept	O
was	O
first	O
introduced	O
when	O
StorageTek	B-Application
(	O
STK	O
)	O
announced	O
their	O
Iceberg	O
product	O
in	O
1991	O
(	O
released	O
later	O
in	O
1994	O
)	O
.	O
</s>
<s>
There	O
is	O
an	O
analogy	O
between	O
thin	B-General_Concept
provisioning	I-General_Concept
in	O
computers	O
and	O
the	O
keeping	O
of	O
cash	O
reserve	O
ratios	O
in	O
banks	O
.	O
</s>
