slots
that
are
controlled
by
this
ESM
as
empty,
and
treats
the
drives
inserted
in
those
slots
as
failed/missing.
For
more
information
about
the
differences
between
the
different
types
of
EXP100s,
see
shows
a
high-level
block
diagram
of
the
EXP100
ESM
failover
architecture.
If
there
are
failures
in
the
Fibre
Channel
data
path
to
an
ESM
in
the
EXP100
storage
expansion
enclosure,
the
DS4000
controller
reroutes
its
data
to
the
ESM
that
it
still
can
access
by
way
of
the
Fibre
Channel
path.
Then,
the
ESM
routes
the
data
to
the
ESM
that
had
Fibre
Channel
connection
problems
using
the
internal
ESM-ESM
data
path.
This
ESM
in
turn
transfers
the
data
to
the
disk
drives
that
it
had
controlled.
Furthermore,
if
one
of
the
ESMs
fails,
the
other
ESMs
assume
control
of
all
the
drives
and
routes
data
to
the
drives
of
the
failed
ESM
using
the
dashed
alternate
paths
shown
in
Unless
there
are
failures
in
both
ESMs
or
there
are
failures
in
the
Fibre
Channel
connections
to
both
ESMs
in
the
EXP100
chassis,
the
controller
and
ESM
firmware
work
together
to
ensure
that
there
is
no
loss
of
data
availability.
shows
that
if
the
Fibre
Channel
connection
to
the
left
ESM
is
bad,
then
the
data
to
drive
1,
which
is
controlled
by
the
left
ESM,
is
routed
through
the
right
ESM
Fibre
Channel
input
connection
to
the
right
ESM,
then
through
the
internal
ESM-ESM
link
to
the
left
ESM,
and
then
to
drive
1.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
left ESM
FC OUT
FC IN
From
controller
drive port or
FC port in
another
EXP100
From
controller
drive port or
FC port in
another
EXP100
To controller
drive port or
FC port in
another
EXP100
To controller
drive port or
FC port in
another
EXP100
Note: Solid lines show normal operation paths. Dashed lines show alternate paths when normal paths fail.
Port Bypass Logic
FibreChannel-SATA
Bridge
FC OUT
FC IN
FibreChannel-SATA
Bridge
right ESM
Internal ESM --
ESM link
Port Bypass Logic
exp12cfg7
Figure
9.
EXP100
ESM
and
drive
paths
Chapter
1.
Introduction
25
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Summary of Contents for TotalStorage EXP100
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