MASS
STORAGE
SUBSYSTEM
Mass
storage for the
CRAY-1
computer system
consists
of
one
or
more
Cray
Research, Inc.
OCU-2
Disk
Controllers
and
multiple
00-19
Disk
Storage Units.
The
disk
controller
is
a
Cray
Research, Inc. product
and
is
implemented
in
flat-pack
ECl
logic
similar
to
that
used
in the
CRAY-1
mainframe.
The
con-
troller
operates synchronously with the
mainframe
over a
16-bit
full-duplex
channel.
The
controller
is
in a
OCC-1
refrigerant-cooled
cabinet located
near the mainframe.
Up
to four
controllers
may
be
contained in a cabinet.
The
cabinet requires about 5 sq.
ft.
of
floor
space
and
is
49
inches high.
Each
controller
may
have
from
one
to four
00-19
disk storage
units
attached
to
it.
Data
passes through the
controller
to or
from
one
disk storage
unit
at
a time.
The
controller
may
be
connected to a
16-bit
minicomputer
station
in addition to the
CRAY-l.
If
this
additional connection
is
made,
the
station
and
mainframe
may
share the
controller
operation.
Either,
but not both,
can
have
an
operation in progress
at
one
time; software
interlocks
must
be
provided
to avoid
conflicts.
Each
of the
00-19
disk storage
units
has
two
ports for
controllers.
A second
independent data path
may
exist
to each disk storage
unit
through another
Cray
Research
controller.
Reservation logic
is
provided to control access
to each disk storage
unit.
Operational
characteristics
of
the
00-19
Disk
Storage Units are
summarized
in Table 2-1. Further information about the
mass
storage subsystem
is
presented in separate publications.
Table 2-1.
Characteristics
of
a
00-19
Disk
Storage Unit
Bit capacity per drive 2.424 x
10
9
Latency 16.6
msec
Tracks per surface
411
Access
time
15
-
80
msec
Sectors per track
18
Data
transfer
rate
Bits per
sector
32,768
(average
bits
per
sec.)
35.4 x
10
6
Number
of
head
groups
10
Total
bits
that
can
be
streamed to a
unit
Recording
surfaces
(disk cylinder capacity) 5.9 x
10
6
per drive
40
2240004
2-8
E
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