![background image](http://html1.mh-extra.com/html/ibm/totalstorage-ds8000/totalstorage-ds8000_user-manual_4109708143.webp)
addition,
in
a
remote
mirror
and
copy
environment,
a
site
where
production
applications
run
might
be
referred
to
as
the
production
site,
local
site,
or
Site
A.
A
site
that
has
mirrored
data
of
your
local
site
might
be
referred
to
as
a
recovery
site,
backup
site,
remote
site,
or
Site
B.
Remote
mirror
and
copy
differs
from
FlashCopy
in
two
essential
ways.
First,
the
source
and
target
volumes
can
be
on
the
same
storage
server
or
on
separate
storage
servers
that
are
located
at
some
distance
from
each
other.
Second,
and
more
significantly,
remote
mirror
and
copy
does
not
capture
the
state
of
the
source
volume
at
some
point
in
time,
but
rather
reflects
all
changes
that
were
made
on
the
source
volume
to
the
target
volume.
The
following
modes
of
operation
are
available:
IBM
TotalStorage
Global
Copy
Global
Copy
copies
data
nonsynchronously
and
over
longer
distance
than
is
possible
with
Metro
Mirror.
In
Global
Copy
mode,
the
source
volume
sends
a
periodic,
incremental
copy
of
updated
tracks
to
the
target
volume
instead
of
a
constant
stream
of
updates.
Because
the
original
order
of
updates
is
not
strictly
maintained,
this
is
considered
a
″
fuzzy
″
copy.
All
updates
that
an
attached
host
performs
on
the
source
volume
are
also
performed
on
the
target
volume,
but
at
a
later
time.
IBM
TotalStorage
Global
Mirror
Global
Mirror
copying
provides
a
two-site
extended
distance
remote
copy
option
for
disaster
recovery.
This
solution
is
based
on
existing
Global
Copy
and
FlashCopy.
With
Global
Mirror,
the
data
that
the
host
writes
to
the
storage
unit
at
the
local
site
is
asynchronously
shadowed
to
the
storage
unit
at
the
remote
site.
A
consistent
copy
of
the
data
is
then
automatically
maintained
on
the
storage
unit
at
the
remote
site.
IBM
TotalStorage
Metro
Mirror
Metro
Mirror
synchronously
mirrors
updates
that
are
done
to
source
volumes.
All
updates
that
any
attached
host
performs
on
the
source
volume
are
also
performed
on
the
target
volume
before
operation
completion
is
indicated.
Metro
Mirror
copying
supports
a
maximum
distance
of
300
km
(186
mi).
Global
Copy
Global
Copy
functions
offer
a
nonsynchronous
long-distance
copy
option
whereby
write
operations
to
a
storage
unit
at
your
production
site
are
considered
complete
before
they
are
transmitted
to
a
storage
unit
at
your
recovery
site.
Global
Copy
is
a
nonsynchronous
mirroring
function
and
is
an
alternative
mirroring
approach
to
Metro
Mirror
operations.
Host
updates
to
the
source
volume
are
not
delayed
by
waiting
for
the
update
to
be
confirmed
by
a
storage
unit
at
your
recovery
site.
The
source
volume
sends
a
periodic,
incremental
copy
of
updated
tracks
to
the
target
volume
instead
of
a
constant
stream
of
updates.
There
is
no
guarantee
that
dependent
write
operations
are
transferred
in
the
same
sequence
that
they
have
been
applied
to
the
source
volume.
This
nonsynchronous
operation
results
in
a
“fuzzy
copy”
at
the
recovery
site;
however,
through
operational
procedures,
you
can
create
a
point-in-time
consistent
copy
at
your
recovery
site
that
is
suitable
for
data
migration,
backup,
and
disaster
recovery
purposes.
To
ensure
that
a
consistent
copy
of
the
data
is
created,
you
can
periodically
switch
from
Global
Copy
to
Metro
Mirror
mode.
Then,
either
stop
application
I/O
or
freeze
Chapter
8.
Optional
feature
codes
for
the
DS8000
117
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