Failover
and
failback
operations
The
failover
operation
is
the
process
of
switching
production
to
a
backup
facility
(normally
your
recovery
site).
A
failback
operation
is
the
process
of
returning
production
to
its
original
location
after
a
disaster
or
a
scheduled
maintenance
period.
There
are
times,
both
planned
and
unplanned,
when
it
is
necessary
to
suspend
disk
mirroring
and
to
make
use
of
the
secondary
storage
unit
in
your
configuration.
As
a
manual
process,
this
can
be
complex.
However,
failover
and
failback
recovery
operations
are
available
to
simplify
this
process
and
reduce
the
risk
of
error
and
the
time
it
takes
to
switch
sites
and
restart
I/O
operations.
Failover
is
the
process
of
temporarily
switching
production
to
a
backup
facility
(normally
your
recovery
site)
following
a
scheduled
maintenance
period
or
a
disaster
at
your
production
(or
local)
site.
A
failover
operation
is
always
followed
by
a
failback
operation,
which
is
the
process
of
returning
production
to
its
original
location.
These
operations
use
remote
mirror
and
copy
functions
to
reduce
the
time
that
is
required
to
synchronize
volumes
after
switching
sites
during
planned
or
unplanned
outages.
The
failover
and
failback
operations
allow
change
recording
to
be
enabled
on
the
target
volumes
without
having
to
communicate
between
the
target
and
source
storage
units.
This
method
eliminates
the
need
to
perform
a
full
volume
copy
from
your
recovery
site
to
the
production
site,
which
can
reduce
the
time
that
is
required
to
resume
operations
at
your
production
site.
In
a
typical
remote
mirror
and
copy
environment,
processing
will
temporarily
failover
to
the
storage
unit
at
your
recovery
site
if
an
outage
occurs
at
the
production
site.
Through
use
of
failover
operations,
the
state
of
a
storage
unit
in
your
target
configuration
changes.
As
a
result,
the
storage
unit
is
recognized
as
the
source
storage
unit
in
the
pair.
Because
the
failover
process
puts
the
volumes
into
a
suspended
state,
changes
are
tracked
within
a
bitmap.
Assuming
that
change
recording
is
enabled,
only
change
data
is
sent
to
the
production
site
to
synchronize
the
volumes,
thereby
reducing
the
time
that
is
required
to
complete
the
failback
operation.
When
it
is
safe
to
return
to
your
production
site,
assuming
that
no
physical
damage
has
occurred
to
the
storage
unit
in
the
location,
you
can
delete
paths
and
create
new
ones
from
your
production
site
to
your
recovery
site.
Then,
you
can
create
a
failback
recovery
request
to
restore
the
storage
unit
as
the
production
storage
unit
in
the
relationship.
The
following
considerations
are
for
failover
and
failback
operations:
v
The
failover
operation
does
not
reverse
the
direction
of
a
remote
mirror
and
copy
pair.
It
changes
a
target
device
into
a
suspended
source
device,
while
leaving
the
source
device
in
its
current
state.
v
The
failback
recovery
operation
can
be
issued
against
any
remote
mirror
and
copy
volume
that
is
in
a
primary
suspended
state.
The
operation
copies
required
data
from
the
source
volume
to
the
target
volume
in
order
to
resume
mirroring.
Failback
operations
are
commonly
used
after
a
failover
operation
has
been
issued
to
restart
mirroring
either
in
the
reverse
direction
(remote
site
to
local
site)
or
in
the
original
direction
(local
site
to
remote
site).
132
DS8000
User’s
Guide
Содержание DS8000 - ADDITIONAL INFORMATION
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