<s>
BackupPC	B-Language
is	O
a	O
free	B-Application
disk-to-disk	O
backup	B-Application
software	I-Application
suite	O
with	O
a	O
web-based	O
frontend	O
.	O
</s>
<s>
The	O
cross-platform	B-Operating_System
server	O
will	O
run	O
on	O
any	O
Linux	B-Application
,	O
Solaris	B-Application
,	O
or	O
UNIX-based	O
server	O
.	O
</s>
<s>
In	O
2007	O
,	O
BackupPC	B-Language
was	O
mentioned	O
as	O
one	O
of	O
the	O
three	O
most	O
well	O
known	O
open-source	O
backup	B-Application
software	I-Application
,	O
even	O
though	O
it	O
is	O
one	O
of	O
the	O
tools	O
that	O
are	O
"	O
so	O
amazing	O
,	O
but	O
unfortunately	O
,	O
if	O
no	O
one	O
ever	O
talks	O
about	O
them	O
,	O
many	O
folks	O
never	O
hear	O
of	O
them	O
"	O
.	O
</s>
<s>
Data	B-General_Concept
deduplication	I-General_Concept
reduces	O
the	O
disk	O
space	O
needed	O
to	O
store	O
the	O
backups	B-Application
in	O
the	O
disk	O
pool	O
.	O
</s>
<s>
It	O
is	O
possible	O
to	O
use	O
it	O
as	O
D2D2T	B-General_Concept
solution	O
,	O
if	O
the	O
archive	O
function	O
of	O
BackupPC	B-Language
is	O
used	O
to	O
back	B-Protocol
up	I-Protocol
the	O
disk	O
pool	O
to	O
tape	O
.	O
</s>
<s>
BackupPC	B-Language
is	O
not	O
a	O
block-level	O
backup	B-Application
system	O
like	O
Ghost4Linux	O
but	O
performs	O
file-based	O
backup	B-Application
and	O
restore	O
.	O
</s>
<s>
Thus	O
it	O
is	O
not	O
suitable	O
for	O
backup	B-Application
of	O
disk	O
images	O
or	O
raw	O
disk	O
partitions	O
.	O
</s>
<s>
BackupPC	B-Language
incorporates	O
a	O
Server	B-Operating_System
Message	I-Operating_System
Block	I-Operating_System
(	O
SMB	O
)	O
client	O
that	O
can	O
be	O
used	O
to	O
back	B-Protocol
up	I-Protocol
network	O
shares	O
of	O
computers	O
running	O
Windows	O
.	O
</s>
<s>
Paradoxically	O
,	O
under	O
such	O
a	O
setup	O
the	O
BackupPC	B-Language
server	O
can	O
be	O
located	O
behind	O
a	O
NAT	B-Protocol
'd	I-Protocol
firewall	O
while	O
the	O
Windows	O
machine	O
operates	O
over	O
a	O
public	O
IP	O
address	O
.	O
</s>
<s>
While	O
this	O
may	O
not	O
be	O
advisable	O
for	O
SMB	O
traffic	O
,	O
it	O
is	O
more	O
useful	O
for	O
web	O
servers	O
running	O
Secure	B-Protocol
Shell	I-Protocol
(	O
SSH	B-Protocol
)	O
with	O
GNU	B-Application
tar	I-Application
and	O
rsync	B-Application
available	O
,	O
as	O
it	O
allows	O
the	O
BackupPC	B-Language
server	O
to	O
be	O
stored	O
in	O
a	O
subnet	O
separate	O
from	O
the	O
web	O
server	O
's	O
DMZ	B-General_Concept
.	O
</s>
<s>
It	O
is	O
published	O
under	O
the	O
GNU	B-License
General	I-License
Public	I-License
License	I-License
.	O
</s>
<s>
BackupPC	B-Language
supports	O
NFS	O
,	O
SSH	B-Protocol
,	O
SMB	O
and	O
rsync	B-Application
.	O
</s>
<s>
It	O
can	O
back	B-Protocol
up	I-Protocol
Unix-like	O
systems	O
with	O
native	O
ssh	B-Protocol
and	O
tar	B-Application
or	O
rsync	B-Application
support	O
,	O
such	O
as	O
Linux	B-Application
,	O
BSD	O
,	O
and	O
OS	O
X	O
,	O
as	O
well	O
as	O
Microsoft	O
Windows	O
shares	O
with	O
minimal	O
configuration	O
.	O
</s>
<s>
On	O
Windows	O
,	O
third	O
party	O
implementations	O
of	O
tar	B-Application
,	O
rsync	B-Application
,	O
and	O
SSH	B-Protocol
(	O
such	O
as	O
Cygwin	B-Language
)	O
are	O
required	O
to	O
utilize	O
those	O
protocols	O
.	O
</s>
<s>
The	O
choice	O
between	O
tar	B-Application
and	O
rsync	B-Application
is	O
dictated	O
by	O
the	O
hardware	O
and	O
bandwidth	O
available	O
to	O
the	O
client	O
.	O
</s>
<s>
Clients	O
backed	O
up	O
by	O
rsync	B-Application
use	O
considerably	O
more	O
CPU	O
time	O
than	O
client	O
machines	O
using	O
tar	B-Application
or	O
SMB	O
.	O
</s>
<s>
Clients	O
using	O
SMB	O
or	O
tar	B-Application
use	O
considerably	O
more	O
bandwidth	O
than	O
clients	O
using	O
rsync	B-Application
.	O
</s>
<s>
Using	O
tar	B-Application
or	O
SMB	O
transfers	O
each	O
file	O
in	O
its	O
entirety	O
,	O
using	O
little	O
CPU	O
but	O
maximum	O
bandwidth	O
.	O
</s>
<s>
The	O
rsync	B-Application
method	O
calculates	O
checksums	O
for	O
each	O
file	O
on	O
both	O
the	O
client	O
and	O
server	O
machines	O
in	O
a	O
way	O
that	O
enables	O
a	O
transfer	O
of	O
just	O
the	O
differences	O
between	O
the	O
two	O
files	O
;	O
this	O
uses	O
more	O
CPU	O
resources	O
,	O
but	O
minimizes	O
bandwidth	O
.	O
</s>
<s>
BackupPC	B-Language
uses	O
a	O
combination	O
of	O
hard	O
links	O
and	O
compression	O
to	O
reduce	O
the	O
total	O
disk	O
space	O
used	O
for	O
files	O
.	O
</s>
<s>
At	O
the	O
first	O
full	B-Protocol
backup	I-Protocol
,	O
all	O
files	O
are	O
transferred	O
to	O
the	O
backend	O
,	O
optionally	O
compressed	O
,	O
and	O
then	O
compared	O
.	O
</s>
<s>
The	O
upshot	O
is	O
that	O
an	O
astute	O
system	B-Application
administrator	I-Application
could	O
potentially	O
back	B-Protocol
up	I-Protocol
ten	O
Windows	O
XP	O
laptops	O
with	O
10	O
GB	O
of	O
data	O
each	O
,	O
and	O
if	O
8	O
GB	O
is	O
repeated	O
on	O
each	O
machine	O
(	O
Office	O
and	O
Windows	O
binary	O
files	O
)	O
would	O
look	O
like	O
100GB	O
is	O
needed	O
,	O
but	O
only	O
28GB	O
(	O
10	O
×	O
2GB	O
+	O
8GB	O
)	O
would	O
be	O
used	O
.	O
</s>
<s>
When	O
browsing	O
the	O
backups	B-Application
,	O
incremental	O
backups	B-Application
are	O
automatically	O
filled	O
back	O
to	O
the	O
previous	O
full	B-Protocol
backup	I-Protocol
.	O
</s>
<s>
So	O
every	O
backup	B-Application
appears	O
to	O
be	O
a	O
full	O
and	O
complete	O
set	O
of	O
data	O
.	O
</s>
<s>
Version	O
4.x	O
can	O
still	O
use	O
V3.x	O
repositories	O
,	O
but	O
all	O
new	O
backups	B-Application
use	O
a	O
new	O
format	O
(	O
seamless	O
upgrade	O
)	O
.	O
</s>
