Figure – IBM TOTALSTORAGE DS4500 User Manual
Page 9
swapping
these
mini-hubs,
you
will
not
need
to
schedule
down
time
later
for
re-cabling
the
drive
loop
if
additional
mini
hubs
are
installed
to
enable
a
second
redundant
drive
loop.
Attention:
Re-cabling
of
drive
loops
to
different
drive
mini
hubs
in
an
operating
DS4500
Storage
Subsystem
configuration
requires
down
time
for
the
configuration.
If
you
have
an
existing
DS4500
Storage
Subsystem
configuration
with
mini
hubs
in
slots
1
and
2
and
you
plan
to
add
an
additional
redundant
drive
loop,
you
must
re-cable
your
existing
configuration
as
shown
in
If
you
can
schedule
down
time
before
you
are
ready
to
add
the
new
drive
loop
in
the
system
(or
whenever
it
is
possible
to
make
the
changes
to
the
mini
hubs
and
the
drive
side
FC
cabling),
you
will
not
have
to
schedule
down
time
when
you
are
ready
to
add
the
new
drive
loop
in
the
system.
Note:
If
you
have
an
existing
DS4500
Storage
Subsystem
configuration
with
mini
hubs
in
slots
1
and
2,
and
you
do
not
plan
to
add
an
additional
redundant
drive
loop,
do
not
make
any
changes
to
the
positions
of
your
mini
hubs.
shows
a
storage
subsystem
containing
one
DS4500
Storage
Subsystem
populated
with
two
mini
hubs
and
one
redundant
drive
loop
with
two
storage
expansion
enclosures,
as
the
DS4500
was
shipped
previously,
with
mini
hubs
installed
in
mini
hub
slots
1
and
2.
“Storage
Expansion
Enclosure
Group
1”
uses
a
redundant
drive
loop
to
connect
to
the
DS4500
Storage
Subsystem.
Loop
A
and
loop
B
make
up
one
redundant
pair
of
drive
loops.
Drive Loop A
Drive Loop B
Drive Loop A Fibre
Channel interface
Cables
Drive Loop B Fibre
Channel interface
Cables
First DS4000 drive
enclosure
Last DS4000 drive
enclosure
Storage Expansion
Enclosures -
Group 1
DS4500 Storage
Subsystem
Input
Input
Output
Output
Drive minihub 4
Drive minihub 2
ds452minb
Figure
7.
Redundant
drive
loop
cabling
overview
with
two
mini
hubs
in
slots
4
and
2
9