<s>
Storage	O
Module	O
Drive	O
(	O
SMD	O
)	O
is	O
a	O
family	O
of	O
storage	O
devices	O
(	O
hard	B-Device
disk	I-Device
drives	I-Device
)	O
that	O
were	O
first	O
shipped	O
by	O
Control	O
Data	O
Corporation	O
in	O
December	O
1973	O
as	O
the	O
CDC	O
9760	O
40	O
MB	O
(	O
unformatted	O
)	O
storage	B-Architecture
module	I-Architecture
disk	I-Architecture
drive	O
.	O
</s>
<s>
It	O
was	O
mainly	O
implemented	O
on	O
disk	O
drives	O
used	O
with	O
mainframes	B-Architecture
and	O
minicomputers	B-Architecture
and	O
was	O
later	O
itself	O
replaced	O
by	O
SCSI	B-Architecture
.	O
</s>
<s>
34	O
sectors	O
of	O
512	O
data	O
bytes	B-Application
each	O
per	O
track	O
is	O
the	O
configuration	O
used	O
on	O
the	O
GEC	B-Device
4000	I-Device
series	I-Device
minicomputers	B-Architecture
.	O
</s>
<s>
SMD	O
disk	B-Operating_System
packs	I-Operating_System
(	O
as	O
the	O
Storage	O
Module	O
itself	O
was	O
most	O
commonly	O
called	O
)	O
required	O
head	O
alignment	O
to	O
assure	O
interchangeability	O
of	O
media	O
between	O
drives	O
.	O
</s>
