Redundant
array
of
independent
disks
(RAID)
is
a
method
of
configuring
multiple
disk
drives
in
a
storage
subsystem
for
high
availability
and
high
performance.
The
collection
of
two
or
more
disk
drives
presents
the
image
of
a
single
disk
drive
to
the
system.
In
the
event
of
a
single
device
failure,
data
can
be
read
or
regenerated
from
the
other
disk
drives
in
the
array.
RAID
implementation
enables
fault-tolerant
data
storage
by
storing
the
data
in
different
places
on
multiple
disk
drive
modules
(DDMs).
By
placing
data
on
multiple
disks,
input/output
operations
can
overlap
in
a
balanced
way
to
improve
the
basic
reliability
and
performance
of
the
attached
storage
devices.
Physical
capacity
can
be
configured
as
RAID
5,
RAID
6
(only
on
the
DS8000
series),
RAID
10,
or
a
combination
of
RAID
5
and
RAID
10.
RAID
5
can
offer
excellent
performance
for
most
applications,
while
RAID
10
can
offer
better
performance
for
selected
applications,
in
particular,
high
random
write
content
applications
in
the
open
systems
environment.
RAID
6
increases
data
protection
by
adding
an
extra
layer
of
parity
over
the
RAID
5
implementation.
You
can
reconfigure
RAID
5
disk
groups
as
RAID
10
disk
groups
or
vice
versa.
RAID
5
overview
RAID
5
is
a
method
of
spreading
volume
data
across
multiple
disk
drives.
The
DS8000
and
DS6000
series
supports
RAID
5
arrays.
RAID
5
increases
performance
by
supporting
concurrent
accesses
to
the
multiple
DDMs
within
each
logical
volume.
Data
protection
is
provided
by
parity,
which
is
stored
throughout
the
drives
in
the
array.
If
a
drive
fails,
the
data
on
that
drive
can
be
restored
using
all
the
other
drives
in
the
array
along
with
the
parity
bits
that
were
created
when
the
data
was
stored.
RAID
6
overview
RAID
6
is
a
method
of
increasing
the
data
protection
of
arrays
with
volume
data
spread
across
multiple
disk
drives.
The
DS8000
series
supports
RAID
6
arrays.
RAID
6
increases
data
protection
by
adding
an
extra
layer
of
parity
over
the
RAID
5
implementation.
By
adding
this
protection,
RAID
6
can
restore
data
from
an
array
with
up
to
two
failed
drives.
The
calculation
and
storage
of
extra
parity
slightly
reduces
the
capacity
and
performance
compared
to
a
RAID
5
array.
RAID
6
is
particularly
suitable
for
storage
using
archive
class
DDMs.
RAID
10
overview
RAID
10
provides
high
availability
by
combining
features
of
RAID
0
and
RAID
1.
The
DS8000
and
DS6000
series
supports
RAID
10
arrays.
RAID
0
increases
performance
by
striping
volume
data
across
multiple
disk
drives.
RAID
1
provides
disk
mirroring
which
duplicates
data
between
two
disk
drives.
By
combining
the
features
of
RAID
0
and
RAID
1,
RAID
10
provides
a
second
optimization
for
fault
tolerance.
RAID
10
implementation
provides
data
mirroring
from
one
DDM
to
another
DDM.
RAID
10
stripes
data
across
half
of
the
disk
drives
in
the
RAID
10
configuration.
The
other
half
of
the
array
mirrors
the
first
set
of
disk
drives.
Access
to
data
is
preserved
if
one
disk
in
each
mirrored
pair
remains
available.
In
some
cases,
RAID
10
offers
faster
data
reads
and
writes
than
RAID
5
because
it
does
not
need
to
22
DS8000
User’s
Guide
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