<s>
Elliptics	B-Application
is	O
a	O
distributed	O
key	O
–	O
value	O
data	O
storage	O
with	O
open	B-Application
source	I-Application
code	I-Application
.	O
</s>
<s>
By	O
default	O
it	O
is	O
a	O
classic	O
distributed	B-Operating_System
hash	I-Operating_System
table	I-Operating_System
(	O
DHT	O
)	O
with	O
multiple	O
replicas	B-Architecture
put	O
in	O
different	O
groups	O
(	O
distributed	O
hashes	O
)	O
.	O
</s>
<s>
Elliptics	B-Application
was	O
created	O
to	O
meet	O
requirements	O
of	O
multi-datacenter	O
and	O
physically	O
distributed	O
storage	O
locations	O
when	O
storing	O
huge	O
amount	O
of	O
medium	O
and	O
large	O
files	O
(	O
1KB	O
up	O
to	O
gigabytes	O
in	O
size	O
,	O
thousands	O
to	O
billions	O
of	O
objects	O
)	O
.	O
</s>
<s>
Elliptics	B-Application
was	O
created	O
in	O
2007	O
,	O
initially	O
as	O
a	O
part	O
of	O
POHMELFS	B-Application
,	O
a	O
cache	B-General_Concept
coherent	I-General_Concept
distributed	B-Protocol
file	I-Protocol
system	I-Protocol
developed	O
by	O
Linux	B-Operating_System
programmer	O
Evgeniy	O
Polyakov	O
.	O
</s>
<s>
POHMELFS	B-Application
was	O
announced	O
on	O
January	O
31	O
,	O
2008	O
,	O
and	O
merged	O
into	O
the	O
staging	O
area	O
of	O
the	O
Linux	B-Operating_System
kernel	I-Operating_System
source	O
tree	O
in	O
version	O
2.6.30	O
,	O
released	O
June	O
9	O
,	O
2009	O
.	O
</s>
<s>
In	O
2008	O
Elliptics	B-Application
separated	O
as	O
an	O
independent	O
project	O
.	O
</s>
<s>
Polyakov	O
tried	O
different	O
approaches	O
to	O
distributed	O
data	O
storage	O
systems	O
,	O
some	O
of	O
them	O
were	O
not	O
suitable	O
because	O
of	O
their	O
complexity	O
and	O
some	O
of	O
them	O
were	O
too	O
far	O
from	O
a	O
real-life	O
(	O
BerkeleyDB	B-Language
,	O
LevelDB	B-Language
,	O
Kyoto	B-Language
Cabinet	I-Language
backends	O
for	O
medium	O
and	O
big	O
files	O
,	O
different	O
datacenters	O
in	O
a	O
single	O
DHT	O
ring	O
,	O
non	O
eventual	O
recovery	O
)	O
.	O
</s>
<s>
Elliptics	B-Application
is	O
eventually	B-General_Concept
consistent	I-General_Concept
system	O
with	O
multiple	O
updated	O
in	O
parallel	O
replicas	B-Architecture
potentially	O
living	O
in	O
physically	O
distributed	O
locations	O
.	O
</s>
<s>
Elliptics	B-Application
contains	O
multiple	O
layers	O
from	O
low-level	O
on-disk	O
store	O
(	O
named	O
Eblob	O
)	O
up	O
to	O
SLRU	O
caches	O
and	O
dynamic	O
routing	O
protocol	O
.	O
</s>
<s>
In	O
2012	O
,	O
Polyakov	O
announced	O
a	O
new	O
version	O
of	O
POHMELFS	B-Application
based	O
on	O
Elliptics	B-Application
.	O
</s>
<s>
As	O
of	O
2014	O
,	O
Elliptics	B-Application
is	O
used	O
in	O
Yandex	B-Operating_System
Maps	I-Operating_System
,	O
Disk	O
,	O
Music	O
,	O
Photos	O
,	O
Market	O
and	O
infrastructure	O
,	O
Sputnik	B-Language
search	I-Language
engine	I-Language
and	O
Coub	O
.	O
</s>
<s>
By	O
default	O
,	O
Elliptics	B-Application
forms	O
a	O
distributed	B-Operating_System
hash	I-Operating_System
table	I-Operating_System
in	O
single	O
group	O
(	O
a	O
replica	B-Architecture
)	O
.	O
</s>
<s>
Group	O
may	O
contains	O
one	O
or	O
many	O
servers	O
as	O
well	O
as	O
physical	O
server	O
can	O
contain	O
multiple	O
elliptics	B-Application
groups	O
(	O
replicas	B-Architecture
)	O
stored	O
on	O
different	O
backends	O
.	O
</s>
<s>
Elliptics	B-Application
supports	O
server-side	O
scripting	O
in	O
C++	B-Language
,	O
JavaScript	B-Language
,	O
Python	B-Language
,	O
based	O
on	O
the	O
Cocaine	B-Application
technology	O
,	O
SLRU	O
cache	O
and	O
multiple	O
pluggable	O
backends	O
(	O
eblob	O
is	O
the	O
fastest	O
for	O
medium	O
and	O
large	O
data	O
and	O
the	O
most	O
popular	O
one	O
)	O
.	O
</s>
<s>
Elliptics	B-Application
clients	O
connect	O
directly	O
to	O
all	O
storage	O
servers	O
which	O
helps	O
to	O
:	O
</s>
<s>
There	O
are	O
several	O
application	B-Application
programming	I-Application
interfaces	I-Application
(	O
APIs	B-Application
)	O
for	O
data	O
access	O
:	O
</s>
<s>
Eventual	B-General_Concept
consistency	I-General_Concept
:	O
as	O
Elliptics	B-Application
is	O
fully	O
distributed	O
in	O
case	O
of	O
emergency	O
server	O
can	O
possibly	O
return	O
a	O
file	O
copy	O
which	O
is	O
older	O
than	O
an	O
actual	O
one	O
.	O
</s>
<s>
API	B-Application
may	O
be	O
inconvenient	O
for	O
high-level	O
requests	O
.	O
</s>
<s>
Elliptics	B-Application
does	O
not	O
provide	O
its	O
users	O
with	O
SQL-like	O
data	O
requests	O
.	O
</s>
<s>
Elliptics	B-Application
does	O
not	O
have	O
high-level	O
transactions	O
support	O
that	O
is	O
why	O
it	O
is	O
impossible	O
to	O
guarantee	O
that	O
a	O
command	O
group	O
will	O
be	O
fully	O
executed	O
or	O
will	O
not	O
be	O
executed	O
at	O
all	O
.	O
</s>
<s>
Elliptics	B-Application
and	O
its	O
supporting	O
projects	O
are	O
being	O
documented	O
at	O
community	O
.	O
</s>
<s>
Elliptics	B-Application
and	O
related	O
projects	O
are	O
discussed	O
in	O
open	O
Google	O
.	O
</s>
