<s>
Spin-up	B-Device
refers	O
to	O
the	O
process	O
of	O
a	O
hard	B-Device
disk	I-Device
drive	I-Device
or	O
optical	B-Device
disc	I-Device
drive	O
accelerating	O
its	O
platters	B-Device
or	O
inserted	O
optical	B-Device
disc	I-Device
from	O
a	O
stopped	O
state	O
to	O
an	O
operational	O
speed	O
.	O
</s>
<s>
The	O
period	O
of	O
time	O
taken	O
by	O
the	O
drive	O
to	O
perform	O
this	O
process	O
is	O
referred	O
to	O
as	O
its	O
spin-up	B-Device
time	O
,	O
the	O
average	O
of	O
which	O
is	O
reported	O
by	O
hard	B-Device
disks	I-Device
as	O
a	O
S.M.A.R.T.	O
</s>
<s>
Typical	O
speeds	O
of	O
hard	B-Device
disks	I-Device
have	O
been	O
2400	O
,	O
3600	O
,	O
4200	O
,	O
5400	O
,	O
7200	O
,	O
10000	O
and	O
15000	O
revolutions	O
per	O
minute	O
(	O
RPM	O
)	O
.	O
</s>
<s>
Operational	O
speed	O
of	O
optical	B-Device
disc	I-Device
drives	O
may	O
vary	O
depending	O
on	O
type	O
of	O
disc	O
and	O
mode	O
of	O
operation	O
(	O
see	O
Constant	B-Device
linear	I-Device
velocity	I-Device
)	O
.	O
</s>
<s>
Spin-up	B-Device
of	O
hard	B-Device
disks	I-Device
generally	O
occurs	O
at	O
the	O
very	O
beginning	O
of	O
the	O
computer	O
boot	B-Operating_System
process	I-Operating_System
.	O
</s>
<s>
A	O
drive	O
in	O
the	O
process	O
of	O
being	O
spun	O
up	O
needs	O
more	O
energy	O
input	O
than	O
a	O
drive	O
that	O
is	O
already	O
spinning	O
at	O
operation	O
speeds	O
,	O
since	O
more	O
effort	O
is	O
required	O
for	O
the	O
electric	O
motor	O
to	O
accelerate	O
the	O
platters	B-Device
,	O
as	O
opposed	O
to	O
maintaining	O
their	O
speed	O
.	O
</s>
<s>
Staggered	O
Spin-up	B-Device
(	O
SSU	O
)	O
and	O
Power-Up	O
In	O
Standby	O
(	O
PUIS	O
)	O
are	O
features	O
that	O
can	O
help	O
control	O
spin-up	B-Device
of	O
multiple	O
drives	O
within	O
a	O
computer	O
system	O
or	O
a	O
disk	B-Device
subsystem	I-Device
.	O
</s>
<s>
Staggered	O
Spin-up	B-Device
(	O
SSU	O
)	O
was	O
introduced	O
into	O
SATA	O
revision	O
2.5	O
in	O
2005	O
.	O
</s>
<s>
SSU	O
allows	O
a	O
SATA	O
host	O
bus	O
adapter	O
to	O
spin	O
up	O
hard	B-Device
drives	I-Device
in	O
a	O
sequential	O
manner	O
.	O
</s>
<s>
Hard	B-Device
drive	I-Device
spin-up	B-Device
requires	O
more	O
power	O
than	O
maintaining	O
operating	O
rotational	O
speed	O
and	O
staggering	O
hard	B-Device
drive	I-Device
spin	O
up	O
in	O
a	O
multiple	O
hard	B-Device
drive	I-Device
system	O
reduces	O
the	O
maximum	O
power	O
needed	O
for	O
hard	B-Device
disk	I-Device
startup	O
.	O
</s>
<s>
Power-up	O
in	O
standby	O
(	O
PUIS	O
)	O
(	O
also	O
called	O
PM2	O
)	O
is	O
used	O
on	O
some	O
Serial	O
ATA	O
(	O
SATA	O
)	O
and	O
Parallel	O
ATA	O
(	O
sometimes	O
called	O
PATA	O
or	O
IDE	O
)	O
hard	B-Device
disk	I-Device
drives	I-Device
.	O
</s>
<s>
PUIS	O
requires	O
BIOS	B-Operating_System
and/or	O
driver	O
support	O
to	O
use	O
.	O
</s>
<s>
When	O
power	O
is	O
applied	O
to	O
the	O
hard	B-Device
disk	I-Device
drive	I-Device
,	O
the	O
drive	O
will	O
not	O
spin-up	B-Device
until	O
a	O
PUIS	O
Spin-Up	B-Device
command	O
is	O
issued	O
.	O
</s>
<s>
The	O
computer	O
system	B-Operating_System
BIOS	I-Operating_System
or	O
RAID	B-Device
controller	I-Device
must	O
issue	O
the	O
command	O
to	O
tell	O
the	O
drive(s )	O
to	O
spin-up	B-Device
before	O
they	O
can	O
be	O
accessed	O
.	O
</s>
<s>
PUIS	O
can	O
be	O
enabled	O
by	O
tools	O
such	O
as	O
hdparm	B-Application
for	O
drives	O
which	O
support	O
this	O
feature	O
.	O
</s>
