<s>
A	O
hybrid	B-General_Concept
array	I-General_Concept
is	O
a	O
form	O
of	O
hierarchical	B-Application
storage	I-Application
management	I-Application
that	O
combines	O
hard	B-Device
disk	I-Device
drives	I-Device
(	O
HDDs	O
)	O
with	O
solid-state	B-Device
drives	I-Device
(	O
SSDs	B-Device
)	O
for	O
I/O	B-General_Concept
speed	O
improvements	O
.	O
</s>
<s>
Hybrid	O
storage	O
arrays	O
aim	O
to	O
mitigate	O
the	O
ever	O
increasing	O
price-performance	O
gap	O
between	O
HDDs	O
and	O
DRAM	O
by	O
adding	O
a	O
non-volatile	O
flash	O
level	O
to	O
the	O
memory	B-General_Concept
hierarchy	I-General_Concept
.	O
</s>
<s>
Hybrid	B-General_Concept
arrays	I-General_Concept
thus	O
aim	O
to	O
lower	O
the	O
cost	O
per	O
I/O	B-General_Concept
,	O
compared	O
to	O
using	O
only	O
SSDs	B-Device
for	O
storage	O
.	O
</s>
<s>
Hybrid	O
architectures	O
can	O
be	O
as	O
simple	O
as	O
involving	O
a	O
single	O
SSD	B-Device
cache	B-General_Concept
for	O
desktop	O
or	O
laptop	O
computers	O
,	O
or	O
can	O
be	O
more	O
complex	O
as	O
configurations	O
for	O
data	B-Operating_System
centers	I-Operating_System
and	O
cloud	B-Architecture
computing	I-Architecture
.	O
</s>
<s>
Some	O
commercial	O
products	O
for	O
building	O
hybrid	B-General_Concept
arrays	I-General_Concept
include	O
:	O
</s>
<s>
Linux	B-Application
software	O
includes	O
bcache	B-Application
,	O
dm-cache	B-Application
,	O
and	O
Flashcache	B-Application
(	O
and	O
its	O
fork	O
EnhanceIO	B-Application
)	O
.	O
</s>
<s>
Condusive	O
's	O
ExpressCache	B-General_Concept
is	O
marketed	O
for	O
laptops	O
.	O
</s>
<s>
Oracle	B-Application
Corporation	I-Application
markets	O
products	O
such	O
as	O
Exadata	B-Device
Smart	O
Cache	B-General_Concept
Flash	O
,	O
and	O
the	O
FS1	O
flash	O
storage	O
system	O
.	O
</s>
<s>
Microsoft	O
ReadyBoost	O
allows	O
personal	O
computers	O
to	O
USB	O
flash	O
drives	O
as	O
cache	B-General_Concept
.	O
</s>
<s>
Nvelo	O
DataPlex	O
SSD	B-Device
caching	I-Device
software	O
was	O
announced	O
in	O
2011	O
,	O
and	O
was	O
acquired	O
by	O
Samsung	B-Application
in	O
2012	O
.	O
</s>
<s>
ZFS	B-Application
using	O
hybrid	O
storage	O
pools	O
,	O
are	O
used	O
for	O
example	O
in	O
some	O
Oracle	B-Application
Corporation	I-Application
products	O
.	O
</s>
