<s>
In	O
information	B-General_Concept
technology	I-General_Concept
,	O
a	O
backup	B-Protocol
,	O
or	O
data	B-Protocol
backup	I-Protocol
is	O
a	O
copy	O
of	O
computer	B-General_Concept
data	I-General_Concept
taken	O
and	O
stored	O
elsewhere	O
so	O
that	O
it	O
may	O
be	O
used	O
to	O
restore	O
the	O
original	O
after	O
a	O
data	B-General_Concept
loss	I-General_Concept
event	O
.	O
</s>
<s>
The	O
verb	O
form	O
,	O
referring	O
to	O
the	O
process	O
of	O
doing	O
so	O
,	O
is	O
"	O
back	B-Protocol
up	I-Protocol
"	O
,	O
whereas	O
the	O
noun	O
and	O
adjective	O
form	O
is	O
"	O
backup	B-Protocol
"	O
.	O
</s>
<s>
Backups	B-Protocol
can	O
be	O
used	O
to	O
recover	O
data	O
after	O
its	O
loss	O
from	O
data	O
deletion	O
or	O
corruption	O
,	O
or	O
to	O
recover	O
data	O
from	O
an	O
earlier	O
time	O
.	O
</s>
<s>
Backups	B-Protocol
provide	O
a	O
simple	O
form	O
of	O
disaster	B-General_Concept
recovery	I-General_Concept
;	O
however	O
not	O
all	O
backup	B-Protocol
systems	O
are	O
able	O
to	O
reconstitute	O
a	O
computer	O
system	O
or	O
other	O
complex	O
configuration	O
such	O
as	O
a	O
computer	B-Architecture
cluster	I-Architecture
,	O
active	B-Protocol
directory	I-Protocol
server	O
,	O
or	O
database	B-Application
server	I-Application
.	O
</s>
<s>
A	O
backup	B-Protocol
system	O
contains	O
at	O
least	O
one	O
copy	O
of	O
all	O
data	O
considered	O
worth	O
saving	O
.	O
</s>
<s>
The	O
data	B-General_Concept
storage	I-General_Concept
requirements	O
can	O
be	O
large	O
.	O
</s>
<s>
An	O
information	B-Protocol
repository	I-Protocol
model	O
may	O
be	O
used	O
to	O
provide	O
structure	O
to	O
this	O
storage	O
.	O
</s>
<s>
There	O
are	O
different	O
types	O
of	O
data	B-General_Concept
storage	I-General_Concept
devices	I-General_Concept
used	O
for	O
copying	O
backups	B-Protocol
of	O
data	O
that	O
is	O
already	O
in	O
secondary	O
storage	O
onto	O
archive	B-Application
files	I-Application
.	O
</s>
<s>
There	O
are	O
also	O
different	O
ways	O
these	O
devices	O
can	O
be	O
arranged	O
to	O
provide	O
geographic	O
dispersion	O
,	O
data	B-General_Concept
security	I-General_Concept
,	O
and	O
portability	B-Application
.	O
</s>
<s>
The	O
process	O
can	O
include	O
methods	O
for	O
dealing	O
with	O
live	O
data	O
,	O
including	O
open	O
files	B-Operating_System
,	O
as	O
well	O
as	O
compression	O
,	O
encryption	O
,	O
and	O
de-duplication	B-General_Concept
.	O
</s>
<s>
Additional	O
techniques	O
apply	O
to	O
enterprise	B-Protocol
client-server	I-Protocol
backup	I-Protocol
.	O
</s>
<s>
Backup	B-Protocol
schemes	O
may	O
include	O
dry	O
runs	O
that	O
validate	O
the	O
reliability	O
of	O
the	O
data	O
being	O
backed	O
up	O
.	O
</s>
<s>
There	O
are	O
limitations	O
and	O
human	O
factors	O
involved	O
in	O
any	O
backup	B-Protocol
scheme	O
.	O
</s>
<s>
A	O
backup	B-Protocol
strategy	O
requires	O
an	O
information	B-Protocol
repository	I-Protocol
,	O
"	O
a	O
secondary	O
storage	O
space	O
for	O
data	O
"	O
that	O
aggregates	O
backups	B-Protocol
of	O
data	O
"	O
sources	O
"	O
.	O
</s>
<s>
The	O
repository	O
could	O
be	O
as	O
simple	O
as	O
a	O
list	O
of	O
all	O
backup	B-Protocol
media	O
(	O
DVDs	O
,	O
etc	O
.	O
)	O
</s>
<s>
and	O
the	O
dates	O
produced	O
,	O
or	O
could	O
include	O
a	O
computerized	O
index	O
,	O
catalog	O
,	O
or	O
relational	B-Application
database	I-Application
.	O
</s>
<s>
The	O
backup	B-Protocol
data	O
needs	O
to	O
be	O
stored	O
,	O
requiring	O
a	O
backup	B-Device
rotation	I-Device
scheme	I-Device
,	O
which	O
is	O
a	O
system	O
of	O
backing	O
up	O
data	O
to	O
computer	O
media	O
that	O
limits	O
the	O
number	O
of	O
backups	B-Protocol
of	O
different	O
dates	O
retained	O
separately	O
,	O
by	O
appropriate	O
re-use	O
of	O
the	O
data	B-General_Concept
storage	I-General_Concept
media	I-General_Concept
by	O
overwriting	O
of	O
backups	B-Protocol
no	O
longer	O
needed	O
.	O
</s>
<s>
The	O
scheme	O
determines	O
how	O
and	O
when	O
each	O
piece	O
of	O
removable	O
storage	O
is	O
used	O
for	O
a	O
backup	B-Protocol
operation	O
and	O
how	O
long	O
it	O
is	O
retained	O
once	O
it	O
has	O
backup	B-Protocol
data	O
stored	O
on	O
it	O
.	O
</s>
<s>
The	O
3-2-1	O
rule	O
can	O
aid	O
in	O
the	O
backup	B-Protocol
process	O
.	O
</s>
<s>
It	O
states	O
that	O
there	O
should	O
be	O
at	O
least	O
3	O
copies	O
of	O
the	O
data	O
,	O
stored	O
on	O
2	O
different	O
types	O
of	O
storage	B-General_Concept
media	I-General_Concept
,	O
and	O
one	O
copy	O
should	O
be	O
kept	O
offsite	O
,	O
in	O
a	O
remote	O
location	O
(	O
this	O
can	O
include	O
cloud	O
storage	O
)	O
.	O
</s>
<s>
2	O
or	O
more	O
different	O
media	O
should	O
be	O
used	O
to	O
eliminate	O
data	B-General_Concept
loss	I-General_Concept
due	O
to	O
similar	O
reasons	O
(	O
for	O
example	O
,	O
optical	O
discs	O
may	O
tolerate	O
being	O
underwater	O
while	O
LTO	O
tapes	O
may	O
not	O
,	O
and	O
SSDs	B-Device
cannot	O
fail	O
due	O
to	O
head	O
crashes	O
or	O
damaged	O
spindle	O
motors	O
since	O
they	O
do	O
n't	O
have	O
any	O
moving	O
parts	O
,	O
unlike	O
hard	B-Device
drives	I-Device
)	O
.	O
</s>
<s>
Disaster	O
protected	O
hard	B-Device
drives	I-Device
like	O
those	O
made	O
by	O
ioSafe	O
are	O
an	O
alternative	O
to	O
an	O
offsite	O
copy	O
,	O
but	O
they	O
have	O
limitations	O
like	O
only	O
being	O
able	O
to	O
resist	O
fire	O
for	O
a	O
limited	O
period	O
of	O
time	O
,	O
so	O
an	O
offsite	O
copy	O
still	O
remains	O
as	O
the	O
ideal	O
choice	O
.	O
</s>
<s>
A	O
repository	O
using	O
this	O
backup	B-Protocol
method	O
contains	O
complete	O
source	O
data	O
copies	O
taken	O
at	O
one	O
or	O
more	O
specific	O
points	O
in	O
time	O
.	O
</s>
<s>
Copying	O
system	B-Operating_System
images	I-Operating_System
,	O
this	O
method	O
is	O
frequently	O
used	O
by	O
computer	O
technicians	O
to	O
record	O
known	O
good	O
configurations	O
.	O
</s>
<s>
However	O
,	O
imaging	O
is	O
generally	O
more	O
useful	O
as	O
a	O
way	O
of	O
deploying	O
a	O
standard	O
configuration	O
to	O
many	O
systems	O
rather	O
than	O
as	O
a	O
tool	O
for	O
making	O
ongoing	O
backups	B-Protocol
of	O
diverse	O
systems	O
.	O
</s>
<s>
An	O
incremental	B-General_Concept
backup	I-General_Concept
stores	O
data	O
changed	O
since	O
a	O
reference	O
point	O
in	O
time	O
.	O
</s>
<s>
Typically	O
a	O
full	B-Protocol
backup	I-Protocol
of	O
all	O
files	B-Operating_System
is	O
made	O
once	O
or	O
at	O
infrequent	O
intervals	O
,	O
serving	O
as	O
the	O
reference	O
point	O
for	O
an	O
incremental	O
repository	O
.	O
</s>
<s>
Subsequently	O
,	O
a	O
number	O
of	O
incremental	B-General_Concept
backups	I-General_Concept
are	O
made	O
after	O
successive	O
time	O
periods	O
.	O
</s>
<s>
Restores	O
begin	O
with	O
the	O
last	O
full	B-Protocol
backup	I-Protocol
and	O
then	O
apply	O
the	O
incrementals	O
.	O
</s>
<s>
Some	O
backup	B-Protocol
systems	O
can	O
create	O
a	O
from	O
a	O
series	O
of	O
incrementals	O
,	O
thus	O
providing	O
the	O
equivalent	O
of	O
frequently	O
doing	O
a	O
full	B-Protocol
backup	I-Protocol
.	O
</s>
<s>
When	O
done	O
to	O
modify	O
a	O
single	O
archive	B-Application
file	I-Application
,	O
this	O
speeds	O
restores	O
of	O
recent	O
versions	O
of	O
files	B-Operating_System
.	O
</s>
<s>
Continuous	B-General_Concept
Data	I-General_Concept
Protection	I-General_Concept
(	O
CDP	O
)	O
refers	O
to	O
a	O
backup	B-Protocol
that	O
instantly	O
saves	O
a	O
copy	O
of	O
every	O
change	O
made	O
to	O
the	O
data	O
.	O
</s>
<s>
Near-CDP	O
backup	B-Protocol
applications	O
—	O
often	O
marketed	O
as	O
"	O
CDP	O
"	O
—	O
automatically	O
take	O
incremental	B-General_Concept
backups	I-General_Concept
at	O
a	O
specific	O
interval	O
,	O
for	O
example	O
every	O
15	O
minutes	O
,	O
one	O
hour	O
,	O
or	O
24	O
hours	O
.	O
</s>
<s>
Near-CDP	O
backup	B-Protocol
applications	O
use	O
journaling	B-Application
and	O
are	O
typically	O
based	O
on	O
periodic	O
"	O
snapshots	B-Application
"	O
,	O
read-only	O
copies	O
of	O
the	O
data	O
frozen	O
at	O
a	O
particular	O
point	O
in	O
time	O
.	O
</s>
<s>
Near-CDP	O
(	O
except	O
for	O
Apple	B-Operating_System
Time	I-Operating_System
Machine	I-Operating_System
)	O
intent-logs	O
every	O
change	O
on	O
the	O
host	O
system	O
,	O
often	O
by	O
saving	O
byte	O
or	O
block-level	O
differences	O
rather	O
than	O
file-level	O
differences	O
.	O
</s>
<s>
This	O
backup	B-Protocol
method	O
differs	O
from	O
simple	O
disk	B-General_Concept
mirroring	I-General_Concept
in	O
that	O
it	O
enables	O
a	O
roll-back	O
of	O
the	O
log	O
and	O
thus	O
a	O
restoration	O
of	O
old	O
images	O
of	O
data	O
.	O
</s>
<s>
Intent-logging	O
allows	O
precautions	O
for	O
the	O
consistency	O
of	O
live	O
data	O
,	O
protecting	O
self-consistent	O
files	B-Operating_System
but	O
requiring	O
applications	O
"	O
be	O
quiesced	O
and	O
made	O
ready	O
for	O
backup.	O
"	O
</s>
<s>
Near-CDP	O
is	O
more	O
practicable	O
for	O
ordinary	O
personal	O
backup	B-Protocol
applications	O
,	O
as	O
opposed	O
to	O
true	O
CDP	O
,	O
which	O
must	O
be	O
run	O
in	O
conjunction	O
with	O
a	O
virtual	O
machine	O
or	O
equivalent	O
and	O
is	O
therefore	O
generally	O
used	O
in	O
enterprise	B-Protocol
client-server	I-Protocol
backups	I-Protocol
.	O
</s>
<s>
Software	O
may	O
create	O
copies	O
of	O
individual	O
files	B-Operating_System
such	O
as	O
written	O
documents	O
,	O
multimedia	O
projects	O
,	O
or	O
user	O
preferences	O
,	O
to	O
prevent	O
failed	O
write	O
events	O
caused	O
by	O
power	O
outages	O
,	O
operating	O
system	O
crashes	O
,	O
or	O
exhausted	O
disk	B-General_Concept
space	I-General_Concept
,	O
from	O
causing	O
data	B-General_Concept
loss	I-General_Concept
.	O
</s>
<s>
A	O
common	O
implementation	O
is	O
an	O
appended	O
"	B-General_Concept
.bak	I-General_Concept
"	I-General_Concept
extension	I-General_Concept
to	O
the	O
file	O
name	O
.	O
</s>
<s>
A	O
Reverse	O
incremental	B-General_Concept
backup	I-General_Concept
method	O
stores	O
a	O
recent	O
archive	B-Application
file	I-Application
"	O
mirror	O
"	O
of	O
the	O
source	O
data	O
and	O
a	O
series	O
of	O
differences	O
between	O
the	O
"	O
mirror	O
"	O
in	O
its	O
current	O
state	O
and	O
its	O
previous	O
states	O
.	O
</s>
<s>
A	O
reverse	O
incremental	B-General_Concept
backup	I-General_Concept
method	O
starts	O
with	O
a	O
non-image	O
full	B-Protocol
backup	I-Protocol
.	O
</s>
<s>
After	O
the	O
full	B-Protocol
backup	I-Protocol
is	O
performed	O
,	O
the	O
system	O
periodically	O
synchronizes	O
the	O
full	B-Protocol
backup	I-Protocol
with	O
the	O
live	O
copy	O
,	O
while	O
storing	O
the	O
data	O
necessary	O
to	O
reconstruct	O
older	O
versions	O
.	O
</s>
<s>
This	O
can	O
either	O
be	O
done	O
using	O
hard	B-Application
links	I-Application
—	O
as	O
Apple	B-Operating_System
Time	I-Operating_System
Machine	I-Operating_System
does	O
,	O
or	O
using	O
binary	O
diffs	B-Application
.	O
</s>
<s>
A	O
differential	B-General_Concept
backup	I-General_Concept
saves	O
only	O
the	O
data	O
that	O
has	O
changed	O
since	O
the	O
last	O
full	B-Protocol
backup	I-Protocol
.	O
</s>
<s>
This	O
means	O
a	O
maximum	O
of	O
two	O
backups	B-Protocol
from	O
the	O
repository	O
are	O
used	O
to	O
restore	O
the	O
data	O
.	O
</s>
<s>
However	O
,	O
as	O
time	O
from	O
the	O
last	O
full	B-Protocol
backup	I-Protocol
(	O
and	O
thus	O
the	O
accumulated	O
changes	O
in	O
data	O
)	O
increases	O
,	O
so	O
does	O
the	O
time	O
to	O
perform	O
the	O
differential	B-General_Concept
backup	I-General_Concept
.	O
</s>
<s>
Restoring	O
an	O
entire	O
system	O
requires	O
starting	O
from	O
the	O
most	O
recent	O
full	B-Protocol
backup	I-Protocol
and	O
then	O
applying	O
just	O
the	O
last	O
differential	B-General_Concept
backup	I-General_Concept
.	O
</s>
<s>
A	O
differential	B-General_Concept
backup	I-General_Concept
copies	O
files	B-Operating_System
that	O
have	O
been	O
created	O
or	O
changed	O
since	O
the	O
last	O
full	B-Protocol
backup	I-Protocol
,	O
regardless	O
of	O
whether	O
any	O
other	O
differential	B-General_Concept
backups	I-General_Concept
have	O
been	O
made	O
since	O
,	O
whereas	O
an	O
incremental	B-General_Concept
backup	I-General_Concept
copies	O
files	B-Operating_System
that	O
have	O
been	O
created	O
or	O
changed	O
since	O
the	O
most	O
recent	O
backup	B-Protocol
of	O
any	O
type	O
(	O
full	O
or	O
incremental	O
)	O
.	O
</s>
<s>
Changes	O
in	O
files	B-Operating_System
may	O
be	O
detected	O
through	O
a	O
more	O
recent	O
date/time	O
of	O
last	O
modification	O
file	B-Application
attribute	I-Application
,	O
and/or	O
changes	O
in	O
file	O
size	O
.	O
</s>
<s>
Other	O
variations	O
of	O
incremental	B-General_Concept
backup	I-General_Concept
include	O
multi-level	O
incrementals	O
and	O
block-level	O
incrementals	O
that	O
compare	O
parts	O
of	O
files	B-Operating_System
instead	O
of	O
just	O
entire	O
files	B-Operating_System
.	O
</s>
<s>
Regardless	O
of	O
the	O
repository	O
model	O
that	O
is	O
used	O
,	O
the	O
data	O
has	O
to	O
be	O
copied	O
onto	O
an	O
archive	B-Application
file	I-Application
data	B-General_Concept
storage	I-General_Concept
medium	I-General_Concept
.	O
</s>
<s>
The	O
medium	O
used	O
is	O
also	O
referred	O
to	O
as	O
the	O
type	O
of	O
backup	B-Protocol
destination	O
.	O
</s>
<s>
Magnetic	B-Architecture
tape	I-Architecture
was	O
for	O
a	O
long	O
time	O
the	O
most	O
commonly	O
used	O
medium	O
for	O
bulk	O
data	B-General_Concept
storage	I-General_Concept
,	O
backup	B-Protocol
,	O
archiving	O
,	O
and	O
interchange	O
.	O
</s>
<s>
Tape	O
is	O
a	O
sequential	B-General_Concept
access	I-General_Concept
medium	O
,	O
so	O
the	O
rate	O
of	O
continuously	O
writing	O
or	O
reading	O
data	O
can	O
be	O
very	O
fast	O
.	O
</s>
<s>
While	O
tape	O
media	O
itself	O
has	O
a	O
low	O
cost	O
per	O
space	O
,	O
tape	O
drives	O
are	O
typically	O
dozens	O
of	O
times	O
as	O
expensive	O
as	O
hard	B-Device
disk	I-Device
drives	I-Device
and	O
optical	O
drives	O
.	O
</s>
<s>
The	O
other	O
remaining	O
viable	O
"	O
super	O
"	O
format	O
is	O
the	O
IBM	B-Device
3592	I-Device
(	O
also	O
referred	O
to	O
as	O
the	O
TS11xx	O
series	O
)	O
.	O
</s>
<s>
The	O
use	O
of	O
hard	B-Device
disk	I-Device
storage	I-Device
has	O
increased	O
over	O
time	O
as	O
it	O
has	O
become	O
progressively	O
cheaper	O
.	O
</s>
<s>
Hard	B-Device
disks	I-Device
are	O
usually	O
easy	O
to	O
use	O
,	O
widely	O
available	O
,	O
and	O
can	O
be	O
accessed	O
quickly	O
.	O
</s>
<s>
However	O
,	O
hard	B-Device
disk	I-Device
backups	B-Protocol
are	O
close-tolerance	O
mechanical	O
devices	O
and	O
may	O
be	O
more	O
easily	O
damaged	O
than	O
tapes	O
,	O
especially	O
while	O
being	O
transported	O
.	O
</s>
<s>
Some	O
manufacturers	O
also	O
offer	O
'	O
ruggedized	O
 '	O
portable	O
hard	B-Device
drives	I-Device
,	O
which	O
include	O
a	O
shock-absorbing	O
case	O
around	O
the	O
hard	B-Device
disk	I-Device
,	O
and	O
claim	O
a	O
range	O
of	O
higher	O
drop	O
specifications	O
.	O
</s>
<s>
Over	O
a	O
period	O
of	O
years	O
the	O
stability	O
of	O
hard	B-Device
disk	I-Device
backups	B-Protocol
is	O
shorter	O
than	O
that	O
of	O
tape	O
backups	B-Protocol
.	O
</s>
<s>
External	O
hard	B-Device
disks	I-Device
can	O
be	O
connected	O
via	O
local	O
interfaces	O
like	O
SCSI	B-Architecture
,	O
USB	B-Protocol
,	O
FireWire	B-Protocol
,	O
or	O
eSATA	O
,	O
or	O
via	O
longer-distance	O
technologies	O
like	O
Ethernet	O
,	O
iSCSI	B-Protocol
,	O
or	O
Fibre	B-Architecture
Channel	I-Architecture
.	O
</s>
<s>
Some	O
disk-based	O
backup	B-Protocol
systems	O
,	O
via	O
Virtual	B-Device
Tape	I-Device
Libraries	I-Device
or	O
otherwise	O
,	O
support	O
data	B-General_Concept
deduplication	I-General_Concept
,	O
which	O
can	O
reduce	O
the	O
amount	O
of	O
disk	O
storage	B-General_Concept
capacity	I-General_Concept
consumed	O
by	O
daily	O
and	O
weekly	O
backup	B-Protocol
data	O
.	O
</s>
<s>
Optical	B-General_Concept
storage	I-General_Concept
uses	O
lasers	O
to	O
store	O
and	O
retrieve	O
data	O
.	O
</s>
<s>
Recordable	O
CDs	B-Device
,	O
DVDs	O
,	O
and	O
Blu-ray	O
Discs	O
are	O
commonly	O
used	O
with	O
personal	O
computers	O
and	O
are	O
generally	O
cheap	O
.	O
</s>
<s>
In	O
the	O
past	O
,	O
the	O
capacities	O
and	O
speeds	O
of	O
these	O
discs	O
have	O
been	O
lower	O
than	O
hard	B-Device
disks	I-Device
or	O
tapes	O
,	O
although	O
advances	O
in	O
optical	O
media	O
are	O
slowly	O
shrinking	O
that	O
gap	O
.	O
</s>
<s>
Potential	O
future	O
data	O
losses	O
caused	O
by	O
gradual	O
media	B-Device
degradation	I-Device
can	O
be	O
predicted	B-Device
by	O
measuring	O
the	O
rate	O
of	O
correctable	O
minor	O
data	O
errors	O
,	O
of	O
which	O
consecutively	O
too	O
many	O
increase	O
the	O
risk	O
of	O
uncorrectable	O
sectors	O
.	O
</s>
<s>
Many	O
optical	O
disc	O
formats	O
are	O
WORM	B-Device
type	O
,	O
which	O
makes	O
them	O
useful	O
for	O
archival	O
purposes	O
since	O
the	O
data	O
cannot	O
be	O
changed	O
.	O
</s>
<s>
Moreover	O
,	O
optical	O
discs	O
are	O
not	B-General_Concept
vulnerable	I-General_Concept
to	O
head	O
crashes	O
,	O
magnetism	O
,	O
imminent	O
water	O
ingress	O
or	O
power	O
surges	O
,	O
and	O
a	O
fault	O
of	O
the	O
drive	O
typically	O
just	O
halts	O
the	O
spinning	O
.	O
</s>
<s>
Optical	O
media	O
is	O
modular	B-Architecture
;	O
the	O
storage	O
controller	O
is	O
not	O
tied	O
to	O
media	O
itself	O
like	O
with	O
hard	B-Device
drives	I-Device
or	O
flash	B-Device
storage	I-Device
(	O
→	O
flash	B-Device
memory	I-Device
controller	I-Device
)	O
,	O
allowing	O
it	O
to	O
be	O
removed	O
and	O
accessed	O
through	O
a	O
different	O
drive	O
.	O
</s>
<s>
However	O
,	O
recordable	B-General_Concept
media	I-General_Concept
may	O
degrade	O
earlier	O
under	O
long-term	O
exposure	O
to	O
light	O
.	O
</s>
<s>
Some	O
optical	B-General_Concept
storage	I-General_Concept
systems	O
allow	O
for	O
cataloged	O
data	B-Protocol
backups	I-Protocol
without	O
human	O
contact	O
with	O
the	O
discs	O
,	O
allowing	O
for	O
longer	O
data	O
integrity	O
.	O
</s>
<s>
A	O
French	O
study	O
in	O
2008	O
indicated	O
that	O
the	O
lifespan	O
of	O
typically-sold	O
CD-Rs	O
was	O
2	O
–	O
10	O
years	O
,	O
but	O
one	O
manufacturer	O
later	O
estimated	O
the	O
longevity	O
of	O
its	O
CD-Rs	O
with	O
a	O
gold-sputtered	O
layer	O
to	O
be	O
as	O
high	O
as	O
100	O
years	O
.	O
</s>
<s>
Sony	O
's	O
proprietary	O
Optical	B-Device
Disc	I-Device
Archive	I-Device
can	O
in	O
2016	O
reach	O
a	O
read	O
rate	O
of	O
250MB/s	O
.	O
</s>
<s>
Solid-state	B-Device
drives	I-Device
(	O
SSDs	B-Device
)	O
use	O
integrated	O
circuit	O
assemblies	O
to	O
store	O
data	O
.	O
</s>
<s>
Flash	B-Device
memory	I-Device
,	O
thumb	O
drives	O
,	O
USB	B-Protocol
flash	O
drives	O
,	O
CompactFlash	B-Device
,	O
SmartMedia	B-Operating_System
,	O
Memory	O
Sticks	O
,	O
and	O
Secure	B-Device
Digital	I-Device
card	I-Device
devices	O
are	O
relatively	O
expensive	O
for	O
their	O
low	O
capacity	O
,	O
but	O
convenient	O
for	O
backing	O
up	O
relatively	O
low	O
data	O
volumes	O
.	O
</s>
<s>
A	O
solid-state	B-Device
drive	I-Device
does	O
not	O
contain	O
any	O
movable	O
parts	O
,	O
making	O
it	O
less	O
susceptible	O
to	O
physical	O
damage	O
,	O
and	O
can	O
have	O
huge	O
throughput	O
of	O
around	O
500	O
Mbit/s	O
up	O
to	O
6	O
Gbit/s	O
.	O
</s>
<s>
Available	O
SSDs	B-Device
have	O
become	O
more	O
capacious	O
and	O
cheaper	O
.	O
</s>
<s>
Flash	B-Device
memory	I-Device
backups	B-Protocol
are	O
stable	O
for	O
fewer	O
years	O
than	O
hard	B-Device
disk	I-Device
backups	B-Protocol
.	O
</s>
<s>
Remote	B-General_Concept
backup	I-General_Concept
services	I-General_Concept
or	O
cloud	B-General_Concept
backups	I-General_Concept
involve	O
service	O
providers	O
storing	O
data	O
offsite	O
.	O
</s>
<s>
This	O
has	O
been	O
used	O
to	O
protect	O
against	O
events	O
such	O
as	O
fires	O
,	O
floods	O
,	O
or	O
earthquakes	O
which	O
could	O
destroy	O
locally	O
stored	O
backups	B-Protocol
.	O
</s>
<s>
Cloud-based	O
backup	B-Protocol
(	O
through	O
services	O
like	O
or	O
similar	O
to	O
Google	B-Application
Drive	I-Application
,	O
and	O
Microsoft	B-Application
OneDrive	I-Application
)	O
provides	O
a	O
layer	O
of	O
data	O
protection	O
.	O
</s>
<s>
Various	O
methods	O
can	O
be	O
used	O
to	O
manage	O
backup	B-Protocol
media	O
,	O
striking	O
a	O
balance	O
between	O
accessibility	O
,	O
security	O
and	O
cost	O
.	O
</s>
<s>
Using	O
on-line	O
disks	O
for	O
staging	B-General_Concept
data	O
before	O
it	O
is	O
sent	O
to	O
a	O
near-line	O
tape	B-Device
library	I-Device
is	O
a	O
common	O
example	O
.	O
</s>
<s>
Online	B-General_Concept
backup	I-General_Concept
storage	O
is	O
typically	O
the	O
most	O
accessible	O
type	O
of	O
data	B-General_Concept
storage	I-General_Concept
,	O
and	O
can	O
begin	O
a	O
restore	O
in	O
milliseconds	O
.	O
</s>
<s>
An	O
internal	O
hard	B-Device
disk	I-Device
or	O
a	O
disk	B-General_Concept
array	I-General_Concept
(	O
maybe	O
connected	O
to	O
SAN	O
)	O
is	O
an	O
example	O
of	O
an	O
online	B-General_Concept
backup	I-General_Concept
.	O
</s>
<s>
Nearline	B-General_Concept
storage	I-General_Concept
is	O
typically	O
less	O
accessible	O
and	O
less	O
expensive	O
than	O
online	O
storage	O
,	O
but	O
still	O
useful	O
for	O
backup	B-Protocol
data	B-General_Concept
storage	I-General_Concept
.	O
</s>
<s>
An	O
example	O
is	O
a	O
tape	B-Device
library	I-Device
with	O
restore	O
times	O
ranging	O
from	O
seconds	O
to	O
a	O
few	O
minutes	O
.	O
</s>
<s>
Off-line	O
storage	O
requires	O
some	O
direct	O
action	O
to	O
provide	O
access	O
to	O
the	O
storage	B-General_Concept
media	I-General_Concept
:	O
for	O
example	O
,	O
inserting	O
a	O
tape	O
into	O
a	O
tape	O
drive	O
or	O
plugging	O
in	O
a	O
cable	O
.	O
</s>
<s>
Because	O
the	O
data	O
is	O
not	O
accessible	O
via	O
any	O
computer	O
except	O
during	O
limited	O
periods	O
in	O
which	O
they	O
are	O
written	O
or	O
read	O
back	O
,	O
they	O
are	O
largely	O
immune	O
to	O
on-line	O
backup	B-Protocol
failure	O
modes	O
.	O
</s>
<s>
Backup	B-Protocol
media	O
may	O
be	O
sent	O
to	O
an	O
off-site	O
vault	O
to	O
protect	O
against	O
a	O
disaster	O
or	O
other	O
site-specific	O
problem	O
.	O
</s>
<s>
The	O
vault	O
can	O
be	O
as	O
simple	O
as	O
a	O
system	O
administrator	O
's	O
home	O
office	O
or	O
as	O
sophisticated	O
as	O
a	O
disaster-hardened	O
,	O
temperature-controlled	O
,	O
high-security	O
bunker	O
with	O
facilities	O
for	O
backup	B-Protocol
media	O
storage	O
.	O
</s>
<s>
A	O
data	O
replica	B-Architecture
can	O
be	O
off-site	O
but	O
also	O
on-line	O
(	O
e.g.	O
,	O
an	O
off-site	O
RAID	B-Architecture
mirror	I-Architecture
)	O
.	O
</s>
<s>
Such	O
a	O
replica	B-Architecture
has	O
fairly	O
limited	O
value	O
as	O
a	O
backup	B-Protocol
.	O
</s>
<s>
A	O
backup	B-General_Concept
site	I-General_Concept
or	O
disaster	B-General_Concept
recovery	I-General_Concept
center	I-General_Concept
is	O
used	O
to	O
store	O
data	O
that	O
can	O
enable	O
computer	O
systems	O
and	O
networks	O
to	O
be	O
restored	O
and	O
properly	O
configure	O
in	O
the	O
event	O
of	O
a	O
disaster	O
.	O
</s>
<s>
A	O
more	O
typical	O
way	O
would	O
be	O
remote	O
disk	B-General_Concept
mirroring	I-General_Concept
,	O
which	O
keeps	O
the	O
DR	O
data	O
as	O
up	O
to	O
date	O
as	O
possible	O
.	O
</s>
<s>
A	O
backup	B-Protocol
operation	O
starts	O
with	O
selecting	O
and	O
extracting	O
coherent	O
units	O
of	O
data	O
.	O
</s>
<s>
Most	O
data	O
on	O
modern	O
computer	O
systems	O
is	O
stored	O
in	O
discrete	O
units	O
,	O
known	O
as	O
files	B-Operating_System
.	O
</s>
<s>
These	O
files	B-Operating_System
are	O
organized	O
into	O
filesystems	B-Application
.	O
</s>
<s>
Deciding	O
what	O
to	O
back	B-Protocol
up	I-Protocol
at	O
any	O
given	O
time	O
involves	O
tradeoffs	O
.	O
</s>
<s>
By	O
backing	O
up	O
too	O
much	O
redundant	O
data	O
,	O
the	O
information	B-Protocol
repository	I-Protocol
will	O
fill	O
up	O
too	O
quickly	O
.	O
</s>
<s>
Copying	B-Application
files	I-Application
:	O
Making	O
copies	O
of	O
files	B-Operating_System
is	O
the	O
simplest	O
and	O
most	O
common	O
way	O
to	O
perform	O
a	O
backup	B-Protocol
.	O
</s>
<s>
A	O
means	O
to	O
perform	O
this	O
basic	O
function	O
is	O
included	O
in	O
all	O
backup	B-Protocol
software	O
and	O
all	O
operating	O
systems	O
.	O
</s>
<s>
Partial	O
file	B-Application
copying	I-Application
:	O
A	O
backup	B-Protocol
may	O
include	O
only	O
the	O
blocks	O
or	O
bytes	O
within	O
a	O
file	O
that	O
have	O
changed	O
in	O
a	O
given	O
period	O
of	O
time	O
.	O
</s>
<s>
This	O
can	O
substantially	O
reduce	O
needed	O
storage	O
space	O
,	O
but	O
requires	O
higher	O
sophistication	O
to	O
reconstruct	O
files	B-Operating_System
in	O
a	O
restore	O
situation	O
.	O
</s>
<s>
Some	O
implementations	O
require	O
integration	O
with	O
the	O
source	O
file	B-Application
system	I-Application
.	O
</s>
<s>
Deleted	O
files	B-Operating_System
:	O
To	O
prevent	O
the	O
unintentional	O
restoration	O
of	O
files	B-Operating_System
that	O
have	O
been	O
intentionally	O
deleted	O
,	O
a	O
record	O
of	O
the	O
deletion	O
must	O
be	O
kept	O
.	O
</s>
<s>
Versioning	O
of	O
files	B-Operating_System
:	O
Most	O
backup	B-Protocol
applications	O
,	O
other	O
than	O
those	O
that	O
do	O
only	O
full	O
only/System	O
imaging	O
,	O
also	O
back	B-Protocol
up	I-Protocol
files	B-Operating_System
that	O
have	O
been	O
modified	O
since	O
the	O
last	O
backup	B-Protocol
.	O
</s>
<s>
"	O
That	O
way	O
,	O
you	O
can	O
retrieve	O
many	O
different	O
versions	O
of	O
a	O
given	O
file	O
,	O
and	O
if	O
you	O
delete	O
it	O
on	O
your	O
hard	B-Device
disk	I-Device
,	O
you	O
can	O
still	O
find	O
it	O
in	O
your	O
[	O
information	O
repository ]	O
archive.	O
"	O
</s>
<s>
Filesystem	B-Application
dump	O
:	O
A	O
copy	O
of	O
the	O
whole	O
filesystem	B-Application
in	O
block-level	O
can	O
be	O
made	O
.	O
</s>
<s>
This	O
is	O
also	O
known	O
as	O
a	O
"	O
raw	O
partition	B-Application
backup	B-Protocol
"	O
and	O
is	O
related	O
to	O
disk	B-Application
imaging	I-Application
.	O
</s>
<s>
The	O
process	O
usually	O
involves	O
unmounting	O
the	O
filesystem	B-Application
and	O
running	O
a	O
program	O
like	O
dd	B-Application
(	O
Unix	O
)	O
.	O
</s>
<s>
Because	O
the	O
disk	O
is	O
read	O
sequentially	O
and	O
with	O
large	O
buffers	O
,	O
this	O
type	O
of	O
backup	B-Protocol
can	O
be	O
faster	O
than	O
reading	O
every	O
file	O
normally	O
,	O
especially	O
when	O
the	O
filesystem	B-Application
contains	O
many	O
small	O
files	B-Operating_System
,	O
is	O
highly	O
fragmented	O
,	O
or	O
is	O
nearly	O
full	O
.	O
</s>
<s>
But	O
because	O
this	O
method	O
also	O
reads	O
the	O
free	O
disk	O
blocks	O
that	O
contain	O
no	O
useful	O
data	O
,	O
this	O
method	O
can	O
also	O
be	O
slower	O
than	O
conventional	O
reading	O
,	O
especially	O
when	O
the	O
filesystem	B-Application
is	O
nearly	O
empty	O
.	O
</s>
<s>
Some	O
filesystems	B-Application
,	O
such	O
as	O
XFS	B-Application
,	O
provide	O
a	O
"	O
dump	O
"	O
utility	O
that	O
reads	O
the	O
disk	O
sequentially	O
for	O
high	O
performance	O
while	O
skipping	O
unused	O
sections	O
.	O
</s>
<s>
The	O
corresponding	O
restore	O
utility	O
can	O
selectively	O
restore	O
individual	O
files	B-Operating_System
or	O
the	O
entire	O
volume	O
at	O
the	O
operator	O
's	O
choice	O
.	O
</s>
<s>
Identification	O
of	O
changes	O
:	O
Some	O
filesystems	B-Application
have	O
an	O
archive	B-Application
bit	O
for	O
each	O
file	O
that	O
says	O
it	O
was	O
recently	O
changed	O
.	O
</s>
<s>
Some	O
backup	B-Protocol
software	O
looks	O
at	O
the	O
date	O
of	O
the	O
file	O
and	O
compares	O
it	O
with	O
the	O
last	O
backup	B-Protocol
to	O
determine	O
whether	O
the	O
file	O
was	O
changed	O
.	O
</s>
<s>
Versioning	B-Application
file	I-Application
system	I-Application
:	O
A	O
versioning	B-Application
filesystem	I-Application
tracks	O
all	O
changes	O
to	O
a	O
file	O
.	O
</s>
<s>
The	O
NILFS	B-Application
versioning	B-Application
filesystem	I-Application
for	O
Linux	O
is	O
an	O
example	O
.	O
</s>
<s>
Files	B-Operating_System
that	O
are	O
actively	O
being	O
updated	O
present	O
a	O
challenge	O
to	O
back	B-Protocol
up	I-Protocol
.	O
</s>
<s>
One	O
way	O
to	O
back	B-Protocol
up	I-Protocol
live	O
data	O
is	O
to	O
temporarily	O
quiesce	B-Device
them	O
(	O
e.g.	O
,	O
close	O
all	O
files	B-Operating_System
)	O
,	O
take	O
a	O
"	O
snapshot	B-Application
"	O
,	O
and	O
then	O
resume	O
live	O
operations	O
.	O
</s>
<s>
At	O
this	O
point	O
the	O
snapshot	B-Application
can	O
be	O
backed	O
up	O
through	O
normal	O
methods	O
.	O
</s>
<s>
A	O
snapshot	B-Application
is	O
an	O
instantaneous	O
function	O
of	O
some	O
filesystems	B-Application
that	O
presents	O
a	O
copy	O
of	O
the	O
filesystem	B-Application
as	O
if	O
it	O
were	O
frozen	O
at	O
a	O
specific	O
point	O
in	O
time	O
,	O
often	O
by	O
a	O
copy-on-write	B-Language
mechanism	O
.	O
</s>
<s>
This	O
is	O
also	O
the	O
case	O
across	O
interrelated	O
files	B-Operating_System
,	O
as	O
may	O
be	O
found	O
in	O
a	O
conventional	O
database	O
or	O
in	O
applications	O
such	O
as	O
Microsoft	B-Operating_System
Exchange	I-Operating_System
Server	I-Operating_System
.	O
</s>
<s>
The	O
term	O
fuzzy	B-Device
backup	I-Device
can	O
be	O
used	O
to	O
describe	O
a	O
backup	B-Protocol
of	O
live	O
data	O
that	O
looks	O
like	O
it	O
ran	O
correctly	O
,	O
but	O
does	O
not	O
represent	O
the	O
state	O
of	O
the	O
data	O
at	O
a	O
single	O
point	O
in	O
time	O
.	O
</s>
<s>
Backup	B-Protocol
options	O
for	O
data	O
files	B-Operating_System
that	O
cannot	O
be	O
or	O
are	O
not	O
quiesced	O
include	O
:	O
</s>
<s>
Open	O
file	O
backup	B-Protocol
:	O
Many	O
backup	B-Protocol
software	O
applications	O
undertake	O
to	O
back	B-Protocol
up	I-Protocol
open	O
files	B-Operating_System
in	O
an	O
internally	O
consistent	O
state	O
.	O
</s>
<s>
Some	O
applications	O
simply	O
check	O
whether	O
open	O
files	B-Operating_System
are	O
in	O
use	O
and	O
try	O
again	O
later	O
.	O
</s>
<s>
Other	O
applications	O
exclude	O
open	O
files	B-Operating_System
that	O
are	O
updated	O
very	O
frequently	O
.	O
</s>
<s>
Interrelated	O
database	O
files	B-Operating_System
backup	B-Protocol
:	O
Some	O
interrelated	O
database	O
file	B-Application
systems	I-Application
offer	O
a	O
means	O
to	O
generate	O
a	O
"	O
hot	O
backup	B-Protocol
"	O
of	O
the	O
database	O
while	O
it	O
is	O
online	O
and	O
usable	O
.	O
</s>
<s>
This	O
may	O
include	O
a	O
snapshot	B-Application
of	O
the	O
data	O
files	B-Operating_System
plus	O
a	O
snapshotted	O
log	O
of	O
changes	O
made	O
while	O
the	O
backup	B-Protocol
is	O
running	O
.	O
</s>
<s>
Upon	O
a	O
restore	O
,	O
the	O
changes	O
in	O
the	O
log	O
files	B-Operating_System
are	O
applied	O
to	O
bring	O
the	O
copy	O
of	O
the	O
database	O
up	O
to	O
the	O
point	O
in	O
time	O
at	O
which	O
the	O
initial	O
backup	B-Protocol
ended	O
.	O
</s>
<s>
Other	O
low-availability	O
interactive	O
applications	O
can	O
be	O
backed	O
up	O
via	O
coordinated	O
snapshots	B-Application
.	O
</s>
<s>
However	O
,	O
genuinely-high-availability	O
interactive	O
applications	O
can	O
be	O
only	O
be	O
backed	O
up	O
via	O
Continuous	B-General_Concept
Data	I-General_Concept
Protection	I-General_Concept
.	O
</s>
<s>
Not	O
all	O
information	O
stored	O
on	O
the	O
computer	O
is	O
stored	O
in	O
files	B-Operating_System
.	O
</s>
<s>
Boot	B-Device
sector	I-Device
:	O
The	O
boot	B-Device
sector	I-Device
can	O
sometimes	O
be	O
recreated	O
more	O
easily	O
than	O
saving	O
it	O
.	O
</s>
<s>
Partition	B-Application
layout	O
:	O
The	O
layout	O
of	O
the	O
original	O
disk	O
,	O
as	O
well	O
as	O
partition	B-Application
tables	O
and	O
filesystem	B-Application
settings	O
,	O
is	O
needed	O
to	O
properly	O
recreate	O
the	O
original	O
system	O
.	O
</s>
<s>
Microsoft	B-Application
Windows	I-Application
keeps	O
a	O
registry	B-Protocol
of	O
system	O
information	O
that	O
is	O
more	O
difficult	O
to	O
restore	O
than	O
a	O
typical	O
file	O
.	O
</s>
<s>
It	O
is	O
frequently	O
useful	O
or	O
required	O
to	O
manipulate	O
the	O
data	O
being	O
backed	O
up	O
to	O
optimize	O
the	O
backup	B-Protocol
process	O
.	O
</s>
<s>
These	O
manipulations	O
can	O
improve	O
backup	B-Protocol
speed	O
,	O
restore	O
speed	O
,	O
data	B-General_Concept
security	I-General_Concept
,	O
media	O
usage	O
and/or	O
reduced	O
bandwidth	O
requirements	O
.	O
</s>
<s>
Out-of-date	O
data	O
can	O
be	O
automatically	O
deleted	O
,	O
but	O
for	O
personal	O
backup	B-Protocol
applications	O
—	O
as	O
opposed	O
to	O
enterprise	B-Protocol
client-server	I-Protocol
backup	I-Protocol
applications	O
where	O
automated	O
data	O
"	O
grooming	O
"	O
can	O
be	O
customized	O
—	O
the	O
deletion	O
can	O
at	O
most	O
be	O
globally	O
delayed	O
or	O
be	O
disabled	O
.	O
</s>
<s>
Various	O
schemes	O
can	O
be	O
employed	O
to	O
shrink	B-General_Concept
the	O
size	O
of	O
the	O
source	O
data	O
to	O
be	O
stored	O
so	O
that	O
it	O
uses	O
less	O
storage	O
space	O
.	O
</s>
<s>
This	O
potentially	O
large	O
reduction	O
is	O
called	O
deduplication	B-General_Concept
.	O
</s>
<s>
It	O
can	O
occur	O
on	O
a	O
server	O
before	O
any	O
data	O
moves	O
to	O
backup	B-Protocol
media	O
,	O
sometimes	O
referred	O
to	O
as	O
source/client	O
side	O
deduplication	B-General_Concept
.	O
</s>
<s>
This	O
approach	O
also	O
reduces	O
bandwidth	O
required	O
to	O
send	O
backup	B-Protocol
data	O
to	O
its	O
target	O
media	O
.	O
</s>
<s>
The	O
process	O
can	O
also	O
occur	O
at	O
the	O
target	O
storage	O
device	O
,	O
sometimes	O
referred	O
to	O
as	O
inline	O
or	O
back-end	O
deduplication	B-General_Concept
.	O
</s>
<s>
Sometimes	O
backups	B-Protocol
are	O
duplicated	B-Architecture
to	O
a	O
second	O
set	O
of	O
storage	B-General_Concept
media	I-General_Concept
.	O
</s>
<s>
This	O
can	O
be	O
done	O
to	O
rearrange	O
the	O
archive	B-Application
files	I-Application
to	O
optimize	O
restore	O
speed	O
,	O
or	O
to	O
have	O
a	O
second	O
copy	O
at	O
a	O
different	O
location	O
or	O
on	O
a	O
different	O
storage	B-General_Concept
medium	I-General_Concept
—	O
as	O
in	O
the	O
disk-to-disk-to-tape	B-General_Concept
capability	O
of	O
Enterprise	B-Protocol
client-server	I-Protocol
backup	I-Protocol
.	O
</s>
<s>
High-capacity	O
removable	O
storage	B-General_Concept
media	I-General_Concept
such	O
as	O
backup	B-Protocol
tapes	I-Protocol
present	O
a	O
data	B-General_Concept
security	I-General_Concept
risk	O
if	O
they	O
are	O
lost	O
or	O
stolen	O
.	O
</s>
<s>
Encrypting	O
the	O
data	O
on	O
these	O
media	O
can	O
mitigate	O
this	O
problem	O
,	O
however	O
encryption	O
is	O
a	O
CPU	O
intensive	O
process	O
that	O
can	O
slow	O
down	O
backup	B-Protocol
speeds	O
,	O
and	O
the	O
security	O
of	O
the	O
encrypted	O
backups	B-Protocol
is	O
only	O
as	O
effective	O
as	O
the	O
security	O
of	O
the	O
key	O
management	O
policy	O
.	O
</s>
<s>
When	O
there	O
are	O
many	O
more	O
computers	O
to	O
be	O
backed	O
up	O
than	O
there	O
are	O
destination	O
storage	O
devices	O
,	O
the	O
ability	O
to	O
use	O
a	O
single	O
storage	O
device	O
with	O
several	O
simultaneous	O
backups	B-Protocol
can	O
be	O
useful	O
.	O
</s>
<s>
However	O
cramming	O
the	O
scheduled	O
backup	B-Protocol
window	O
via	O
"	O
multiplexed	O
backup	B-Protocol
"	O
is	O
only	O
used	O
for	O
tape	O
destinations	O
.	O
</s>
<s>
The	O
process	O
of	O
rearranging	O
the	O
sets	O
of	O
backups	B-Protocol
in	O
an	O
archive	B-Application
file	I-Application
is	O
known	O
as	O
refactoring	O
.	O
</s>
<s>
For	O
example	O
,	O
if	O
a	O
backup	B-Protocol
system	O
uses	O
a	O
single	O
tape	O
each	O
day	O
to	O
store	O
the	O
incremental	B-General_Concept
backups	I-General_Concept
for	O
all	O
the	O
protected	O
computers	O
,	O
restoring	O
one	O
of	O
the	O
computers	O
could	O
require	O
many	O
tapes	O
.	O
</s>
<s>
Refactoring	O
could	O
be	O
used	O
to	O
consolidate	O
all	O
the	O
backups	B-Protocol
for	O
a	O
single	O
computer	O
onto	O
a	O
single	O
tape	O
,	O
creating	O
a	O
"	O
synthetic	O
full	B-Protocol
backup	I-Protocol
"	O
.	O
</s>
<s>
This	O
is	O
especially	O
useful	O
for	O
backup	B-Protocol
systems	O
that	O
do	O
incrementals	O
forever	O
style	O
backups	B-Protocol
.	O
</s>
<s>
Sometimes	O
backups	B-Protocol
are	O
copied	O
to	O
a	O
staging	B-General_Concept
disk	O
before	O
being	O
copied	O
to	O
tape	O
.	O
</s>
<s>
This	O
process	O
is	O
sometimes	O
referred	O
to	O
as	O
D2D2T	B-General_Concept
,	O
an	O
acronym	O
for	O
Disk-to-disk-to-tape	B-General_Concept
.	O
</s>
<s>
It	O
can	O
be	O
useful	O
if	O
there	O
is	O
a	O
problem	O
matching	O
the	O
speed	O
of	O
the	O
final	O
destination	O
device	O
with	O
the	O
source	O
device	O
,	O
as	O
is	O
frequently	O
faced	O
in	O
network-based	O
backup	B-Protocol
systems	O
.	O
</s>
<s>
The	O
most	O
desirable	O
RPO	O
would	O
be	O
the	O
point	O
just	O
prior	O
to	O
the	O
data	B-General_Concept
loss	I-General_Concept
event	O
.	O
</s>
<s>
Making	O
a	O
more	O
recent	O
recovery	O
point	O
achievable	O
requires	O
increasing	O
the	O
frequency	O
of	O
synchronization	B-Application
between	O
the	O
source	O
data	O
and	O
the	O
backup	B-Protocol
repository	O
.	O
</s>
<s>
Data	B-General_Concept
security	I-General_Concept
:	O
In	O
addition	O
to	O
preserving	O
access	O
to	O
data	O
for	O
its	O
owners	O
,	O
data	O
must	O
be	O
restricted	O
from	O
unauthorized	O
access	O
.	O
</s>
<s>
Backups	B-Protocol
must	O
be	O
performed	O
in	O
a	O
manner	O
that	O
does	O
not	O
compromise	O
the	O
original	O
owner	O
's	O
undertaking	O
.	O
</s>
<s>
Data	O
retention	O
period	O
:	O
Regulations	O
and	O
policy	O
can	O
lead	O
to	O
situations	O
where	O
backups	B-Protocol
are	O
expected	O
to	O
be	O
retained	O
for	O
a	O
particular	O
period	O
,	O
but	O
not	O
any	O
further	O
.	O
</s>
<s>
Retaining	O
backups	B-Protocol
after	O
this	O
period	O
can	O
lead	O
to	O
unwanted	O
liability	O
and	O
sub-optimal	O
use	O
of	O
storage	B-General_Concept
media	I-General_Concept
.	O
</s>
<s>
Checksum	B-Algorithm
or	O
hash	B-Error_Name
function	I-Error_Name
validation	O
:	O
Applications	O
that	O
back	B-Protocol
up	I-Protocol
to	O
tape	O
archive	B-Application
files	I-Application
need	O
this	O
option	O
to	O
verify	O
that	O
the	O
data	O
was	O
accurately	O
copied	O
.	O
</s>
<s>
Backup	B-Protocol
process	O
monitoring	O
:	O
Enterprise	B-Protocol
client-server	I-Protocol
backup	I-Protocol
applications	O
need	O
a	O
user	O
interface	O
that	O
allows	O
administrators	O
to	O
monitor	O
the	O
backup	B-Protocol
process	O
,	O
and	O
proves	O
compliance	O
to	O
regulatory	O
bodies	O
outside	O
the	O
organization	O
;	O
for	O
example	O
,	O
an	O
insurance	O
company	O
in	O
the	O
USA	O
might	O
be	O
required	O
under	O
HIPAA	O
to	O
demonstrate	O
that	O
its	O
client	O
data	O
meet	O
records	O
retention	O
requirements	O
.	O
</s>
<s>
User-initiated	O
backups	B-Protocol
and	O
restores	O
:	O
To	O
avoid	O
or	O
recover	O
from	O
minor	O
disasters	O
,	O
such	O
as	O
inadvertently	O
deleting	O
or	O
overwriting	O
the	O
"	O
good	O
"	O
versions	O
of	O
one	O
or	O
more	O
files	B-Operating_System
,	O
the	O
computer	O
user	O
—	O
rather	O
than	O
an	O
administrator	O
—	O
may	O
initiate	O
backups	B-Protocol
and	O
restores	O
(	O
from	O
not	O
necessarily	O
the	O
most-recent	O
backup	B-Protocol
)	O
of	O
files	B-Operating_System
or	O
folders	O
.	O
</s>
