<s>
better	O
performance	O
than	O
LRU	B-General_Concept
(	O
least	O
recently	O
used	O
)	O
.	O
</s>
<s>
Basic	O
LRU	B-General_Concept
maintains	O
an	O
ordered	O
list	O
(	O
the	O
cache	O
directory	O
)	O
of	O
resource	O
entries	O
in	O
the	O
cache	O
,	O
with	O
the	O
sort	O
order	O
based	O
on	O
the	O
time	O
of	O
most	O
recent	O
access	O
.	O
</s>
<s>
ARC	O
improves	O
the	O
basic	O
LRU	B-General_Concept
strategy	O
by	O
splitting	O
the	O
cache	O
directory	O
into	O
two	O
lists	O
,	O
T1	O
and	O
T2	O
,	O
for	O
recently	O
and	O
frequently	O
referenced	O
entries	O
.	O
</s>
<s>
The	O
combined	O
cache	O
directory	O
is	O
organised	O
in	O
four	O
LRU	B-General_Concept
lists	O
:	O
</s>
<s>
ARC	O
is	O
currently	O
deployed	O
in	O
IBM	O
's	O
DS6000/DS8000	O
storage	O
controllers	O
.	O
</s>
<s>
Sun	O
Microsystems	O
's	O
scalable	O
file	O
system	O
ZFS	B-Application
uses	O
a	O
variant	O
of	O
ARC	O
as	O
an	O
alternative	O
to	O
the	O
traditional	O
Solaris	B-Application
filesystem	O
page	O
cache	O
in	O
virtual	O
memory	O
.	O
</s>
<s>
PostgreSQL	B-Application
used	O
ARC	O
in	O
its	O
buffer	O
manager	O
for	O
a	O
brief	O
time	O
(	O
version	O
8.0.0	O
)	O
,	O
but	O
quickly	O
replaced	O
it	O
with	O
another	O
algorithm	O
,	O
</s>
<s>
It	O
uses	O
A	O
variant	O
of	O
ARC	O
in	O
its	O
Caching	B-General_Concept
Algorithm	I-General_Concept
.	O
</s>
<s>
OpenZFS	B-Operating_System
supports	O
using	O
ARC	O
and	O
L2ARC	B-Application
in	O
a	O
multi-level	O
cache	O
as	O
read	O
caches	O
.	O
</s>
<s>
In	O
OpenZFS	B-Operating_System
,	O
disk	O
reads	O
often	O
hit	O
the	O
first	O
level	O
disk	O
cache	O
in	O
RAM	O
using	O
ARC	O
.	O
</s>
<s>
If	O
a	O
SSD	O
is	O
set	O
up	O
to	O
store	O
the	O
second	O
level	O
disk	O
cache	O
,	O
it	O
is	O
called	O
an	O
L2ARC	B-Application
.	O
</s>
<s>
L2ARC	B-Application
uses	O
the	O
same	O
ARC	O
algorithm	O
,	O
but	O
instead	O
of	O
storing	O
the	O
cached	O
data	O
in	O
RAM	O
,	O
L2ARC	B-Application
stores	O
the	O
cached	O
data	O
in	O
a	O
fast	O
SSD	O
.	O
</s>
