<s>
Quantcast	B-Language
File	I-Language
System	I-Language
(	O
QFS	O
)	O
is	O
an	O
open-source	O
distributed	B-Protocol
file	I-Protocol
system	I-Protocol
software	O
package	O
for	O
large-scale	O
MapReduce	B-Operating_System
or	O
other	O
batch-processing	O
workloads	O
.	O
</s>
<s>
It	O
was	O
designed	O
as	O
an	O
alternative	O
to	O
the	O
Apache	B-Application
Hadoop	I-Application
Distributed	B-Protocol
File	I-Protocol
System	I-Protocol
(	O
HDFS	O
)	O
,	O
intended	O
to	O
deliver	O
better	O
performance	O
and	O
cost-efficiency	O
for	O
large-scale	O
processing	O
clusters	O
.	O
</s>
<s>
QFS	O
is	O
software	O
that	O
runs	O
on	O
a	O
cluster	O
of	O
hundreds	O
or	O
thousands	O
of	O
commodity	O
Linux	B-Application
servers	O
and	O
allows	O
other	O
software	O
layers	O
to	O
interact	O
with	O
them	O
as	O
if	O
they	O
were	O
one	O
giant	O
hard	O
drive	O
.	O
</s>
<s>
A	O
client	O
component	O
is	O
the	O
interface	O
point	O
that	O
presents	O
a	O
file	O
system	O
application	B-Application
programming	I-Application
interface	I-Application
(	O
API	B-Application
)	O
to	O
other	O
layers	O
of	O
the	O
software	O
.	O
</s>
<s>
QFS	O
meets	O
it	O
with	O
Reed	B-Error_Name
–	I-Error_Name
Solomon	I-Error_Name
error	I-Error_Name
correction	I-Error_Name
.	O
</s>
<s>
The	O
form	O
of	O
Reed	B-Error_Name
–	I-Error_Name
Solomon	I-Error_Name
encoding	O
used	O
in	O
QFS	O
stores	O
redundant	O
data	O
in	O
nine	O
places	O
and	O
can	O
reconstruct	O
the	O
file	O
from	O
any	O
six	O
of	O
these	O
stripes	O
.	O
</s>
<s>
QFS	O
is	O
written	O
in	O
the	O
programming	O
language	O
C++	B-Language
,	O
operates	O
within	O
a	O
fixed	O
memory	O
footprint	O
,	O
and	O
uses	O
direct	O
input	O
and	O
output	O
(	O
I/O	O
)	O
.	O
</s>
<s>
Quantcast	B-Protocol
adopted	O
KFS	O
in	O
2007	O
,	O
built	O
its	O
own	O
improvements	O
on	O
it	O
over	O
the	O
next	O
several	O
years	O
,	O
and	O
released	O
QFS	O
1.0	O
as	O
an	O
open	O
source	O
project	O
in	O
September	O
,	O
2012	O
.	O
</s>
