<s>
The	O
IBM	B-Application
SAN	I-Application
Volume	I-Application
Controller	I-Application
(	O
SVC	O
)	O
is	O
a	O
block	O
storage	B-Application
virtualization	I-Application
appliance	O
that	O
belongs	O
to	O
the	O
IBM	B-Application
System	I-Application
Storage	I-Application
product	O
family	O
.	O
</s>
<s>
SVC	O
implements	O
an	O
indirection	O
,	O
or	O
"	O
virtualization	O
"	O
,	O
layer	O
in	O
a	O
Fibre	B-Architecture
Channel	I-Architecture
storage	O
area	O
network	O
(	O
SAN	O
)	O
.	O
</s>
<s>
The	O
IBM	B-Application
2145	I-Application
SAN	O
Volume	O
Controller	O
(	O
SVC	O
)	O
is	O
an	O
inline	O
virtualization	O
or	O
"	O
gateway	O
"	O
device	O
.	O
</s>
<s>
It	O
logically	O
sits	O
between	O
hosts	O
and	O
storage	B-General_Concept
arrays	I-General_Concept
,	O
presenting	O
itself	O
to	O
hosts	O
as	O
the	O
storage	O
provider	O
(	O
target	O
)	O
and	O
presenting	O
itself	O
to	O
storage	B-General_Concept
arrays	I-General_Concept
as	O
one	O
big	O
host	O
.	O
</s>
<s>
All	O
advanced	O
functions	O
are	O
therefore	O
implemented	O
in	O
the	O
virtualization	O
layer	O
,	O
which	O
allows	O
switching	O
storage	B-General_Concept
array	I-General_Concept
vendors	O
without	O
impact	O
.	O
</s>
<s>
Nodes	O
are	O
rack-mounted	B-Application
appliances	O
derived	O
from	O
IBM	B-Operating_System
System	I-Operating_System
x	I-Operating_System
servers	O
,	O
protected	O
by	O
redundant	O
power	O
supplies	O
and	O
integrated	O
batteries	O
.	O
</s>
<s>
Each	O
node	O
has	O
Fibre	B-Architecture
Channel	I-Architecture
ports	O
simultaneously	O
used	O
for	O
incoming	O
,	O
outgoing	O
,	O
and	O
intracluster	O
data	O
traffic	O
.	O
</s>
<s>
Intracluster	O
communication	O
includes	O
maintaining	O
read/write	O
cache	B-General_Concept
integrity	O
,	O
sharing	O
status	O
information	O
,	O
and	O
forwarding	O
reads	O
and	O
writes	O
to	O
any	O
port	O
.	O
</s>
<s>
Write	O
cache	B-General_Concept
is	O
protected	O
by	O
mirroring	O
within	O
a	O
pair	O
of	O
SVC	O
nodes	O
,	O
called	O
I/O	O
group	O
.	O
</s>
<s>
Path	O
or	O
board	O
failures	O
are	O
compensated	O
by	O
non-disruptive	O
failover	B-General_Concept
within	O
each	O
I/O	O
group	O
,	O
or	O
optionally	O
across	O
dispersed	O
I/O	O
groups	O
.	O
</s>
<s>
Hosts	O
must	O
have	O
multipath	B-General_Concept
drivers	O
installed	O
,	O
such	O
as	O
IBM	O
Subsystem	O
Device	O
Driver	O
(	O
SDD	O
)	O
or	O
standard	O
MPIO	B-General_Concept
drivers	O
.	O
</s>
<s>
Service	O
IP	B-Protocol
address	I-Protocol
-	O
an	O
IP	B-Protocol
address	I-Protocol
used	O
to	O
service	O
an	O
individual	O
node	O
.	O
</s>
<s>
Configuration	O
node	O
-	O
a	O
single	O
node	O
that	O
holds	O
the	O
cluster	O
's	O
configuration	O
and	O
has	O
the	O
assigned	O
cluster	O
IP	B-Protocol
address	I-Protocol
.	O
</s>
<s>
Web	O
based	O
administration	O
is	O
done	O
directly	O
on	O
the	O
configuration	O
node	O
,	O
using	O
a	O
HTML5	B-Application
GUI	O
.	O
</s>
<s>
Virtual	O
Disk	O
(	O
VDisk	B-Application
)	O
-	O
a	O
unit	O
of	O
storage	O
presented	O
to	O
the	O
host	O
.	O
</s>
<s>
The	O
release	O
6	O
GUI	O
refers	O
to	O
a	O
VDisk	B-Application
as	O
a	O
Volume	O
.	O
</s>
<s>
Managed	O
Disk	O
(	O
MDisk	O
)	O
-	O
a	O
unit	O
of	O
storage	O
(	O
a	O
LUN	O
)	O
from	O
a	O
real	O
,	O
external	O
disk	B-General_Concept
array	I-General_Concept
,	O
virtualized	O
by	O
the	O
SVC	O
.	O
</s>
<s>
An	O
MDisk	O
is	O
the	O
base	O
to	O
create	O
an	O
image	O
mode	O
VDisk	B-Application
.	O
</s>
<s>
The	O
extents	O
of	O
the	O
MDisks	O
in	O
an	O
MDisk	O
Group	O
are	O
the	O
base	O
to	O
create	O
a	O
striped	O
or	O
sequential	O
mode	O
VDisk	B-Application
.	O
</s>
<s>
Extent	O
-	O
a	O
discrete	O
unit	O
of	O
storage	O
;	O
an	O
MDisk	O
is	O
divided	O
into	O
extents	O
;	O
a	O
VDisk	B-Application
is	O
formed	O
from	O
set	O
of	O
extents	O
.	O
</s>
<s>
Release	O
6.2	O
of	O
the	O
SVC	O
held	O
the	O
Storage	O
Performance	O
Council	O
(	O
SPC	O
)	O
world	O
record	O
for	O
SPC-1	O
performance	O
benchmarks	O
,	O
returning	O
over	O
500K	O
(	O
520,043	O
.99	O
)	O
IOPS	O
(	O
I/Os	O
per	O
second	O
)	O
using	O
8	O
SVC	O
nodes	O
and	O
Storwize	B-Device
V7000	O
as	O
the	O
backend	O
disk	O
.	O
</s>
<s>
Release	O
7.x	O
provides	O
multiple	O
enhancements	O
including	O
support	O
for	O
additional	O
CPUs	O
,	O
cache	B-General_Concept
and	O
adapters	O
.	O
</s>
<s>
The	O
streamlined	O
cache	B-General_Concept
operates	O
at	O
100µs	O
fall-through	O
latency	O
and	O
60	O
µs	O
cache-hit	O
latency	O
,	O
enabling	O
SVC	O
as	O
a	O
front-end	O
to	O
IBM	B-Device
FlashSystem	I-Device
solid-state	O
storage	O
without	O
significant	O
performance	O
penalty	O
.	O
</s>
<s>
(	O
See	O
also	O
:	O
FlashSystem	B-Device
V9000	O
)	O
.	O
</s>
<s>
Write	O
and	O
read	O
caching	B-General_Concept
remain	O
active	O
.	O
</s>
<s>
Writes	O
from	O
hosts	O
are	O
acknowledged	O
once	O
they	O
have	O
been	O
committed	O
into	O
the	O
SVC	O
mirrored	O
cache	B-General_Concept
,	O
but	O
prior	O
to	O
being	O
destaged	O
to	O
the	O
underlying	O
storage	O
controllers	O
.	O
</s>
<s>
Cache	B-General_Concept
size	O
is	O
dependent	O
on	O
the	O
SVC	O
hardware	O
model	O
and	O
installed	O
options	O
.	O
</s>
<s>
Fast-write	O
cache	B-General_Concept
is	O
especially	O
useful	O
to	O
increase	O
performance	O
in	O
midrange	O
storage	O
configurations	O
.	O
</s>
<s>
Cache	B-General_Concept
unfriendly	O
"	O
hot	O
"	O
data	O
is	O
dynamically	O
moved	O
to	O
solid	O
state	O
drives	O
SSD	O
,	O
whereas	O
cache	B-General_Concept
friendly	O
data	O
as	O
well	O
as	O
"	O
cold	O
"	O
data	O
is	O
moved	O
to	O
economic	O
spinning	O
disks	O
.	O
</s>
<s>
User-side	O
operations	O
like	O
Snapshot	B-Application
or	O
LUN	O
Resizing	O
apply	O
at	O
the	O
logical	O
instance	O
level	O
.	O
</s>
<s>
Unlike	O
in	O
classical	O
mirroring	O
,	O
logical	O
LUNs	O
are	O
readable	O
and	O
writable	O
on	O
both	O
sides	O
(	O
tandem	O
)	O
at	O
the	O
same	O
time	O
,	O
removing	O
the	O
need	O
for	O
failover	B-General_Concept
,	O
role	O
switch	O
,	O
or	O
site	O
switch	O
as	O
found	O
in	O
Site	O
Recovery	O
managing	O
products	O
.	O
</s>
<s>
The	O
feature	O
can	O
be	O
combined	O
with	O
Live	B-General_Concept
Partition	I-General_Concept
Mobility	I-General_Concept
or	O
VMotion	O
to	O
avoid	O
bulk	O
data	O
transport	O
during	O
a	O
metro-distance	O
virtual	O
server	O
motion	O
.	O
</s>
<s>
For	O
instance	O
,	O
cache	B-General_Concept
write	O
destaging	O
to	O
storage	O
devices	O
is	O
always	O
performed	O
by	O
the	O
most	O
nearby	O
cache	B-General_Concept
copy	O
,	O
unless	O
its	O
peer	O
cache	B-General_Concept
copy	O
is	O
down	O
.	O
</s>
<s>
A	O
Stretched	O
Cluster	O
that	O
maintains	O
an	O
additional	O
synchronous	O
or	O
asynchronous	O
data	O
copy	O
on	O
an	O
independent	O
Stretched	O
Cluster	O
or	O
SVC	O
or	O
Storwize	B-Device
device	O
at	O
geo	O
distances	O
.	O
</s>
<s>
It	O
relies	O
on	O
licensed	O
Metro	O
-	O
or	O
Global	B-Application
Mirror	I-Application
functionality	O
.	O
</s>
<s>
The	O
ability	O
to	O
seamlessly	O
fail	B-General_Concept
over	I-General_Concept
data	O
access	O
between	O
geographically	O
dispersed	O
IO	O
groups	O
or	O
clusters	O
.	O
</s>
<s>
As	O
with	O
Stretched	O
Cluster	O
,	O
both	O
sides	O
accept	O
simultaneous	O
writes	O
,	O
but	O
write	O
cache	B-General_Concept
data	O
is	O
mirrored	O
locally	O
in	O
both	O
sites	O
as	O
IO	O
groups	O
are	O
kept	O
together	O
.	O
</s>
<s>
Hyperswap	O
can	O
be	O
combined	O
with	O
Live	B-General_Concept
Partition	I-General_Concept
Mobility	I-General_Concept
or	O
VMotion	O
for	O
maximized	O
application	O
availability	O
.	O
</s>
<s>
On	O
the	O
server	O
side	O
,	O
Hyperswap	O
works	O
with	O
most	O
native	O
multipath	B-General_Concept
drivers	O
with	O
ALUA	O
support	O
.	O
</s>
<s>
Hyperswap	O
relies	O
on	O
Metro	B-Device
Mirror	I-Device
functionality	O
and	O
requires	O
a	O
Metro	B-Device
Mirror	I-Device
license	O
,	O
as	O
well	O
as	O
a	O
minimum	O
of	O
two	O
node	O
pairs	O
.	O
</s>
<s>
Swift	O
-	O
and	O
S3-compatible	O
object	O
datastores	O
can	O
be	O
used	O
as	O
a	O
cold	O
tier	O
for	O
incremental	O
volume	O
snapshots	B-Application
and	O
volume	O
archives	O
without	O
live	O
production	O
access	O
.	O
</s>
<s>
The	O
temporal	B-General_Concept
locality	I-General_Concept
of	O
the	O
algorithm	O
can	O
even	O
increase	O
the	O
read	O
performance	O
on	O
adequate	O
data	O
patterns	O
such	O
as	O
SQL	O
databases	O
stored	O
on	O
spinning	O
disks	O
.	O
</s>
<s>
The	O
compression	O
efficiency	O
is	O
equal	O
to	O
"	O
zip	O
"	O
(	O
Lempel	B-Algorithm
–	I-Algorithm
Ziv	I-Algorithm
–	I-Algorithm
Welch	I-Algorithm
)	O
with	O
a	O
very	O
large	O
dictionary	O
,	O
and	O
can	O
accurately	O
be	O
predicted	O
across	O
Petabytes	O
using	O
the	O
Comprestimator	O
tool	O
.	O
</s>
<s>
It	O
was	O
initially	O
invented	O
by	O
the	O
acquired	O
startup	O
Storwize	B-Device
Inc.	O
,	O
which	O
also	O
served	O
as	O
new	O
name	O
for	O
the	O
SVC-derived	O
IBM	B-Application
storage	I-Application
systems	O
family	O
.	O
</s>
<s>
This	O
is	O
used	O
to	O
create	O
a	O
disk	B-Application
snapshot	I-Application
for	O
backup/rollback	O
or	O
application	O
testing	O
of	O
a	O
single	O
volume	O
.	O
</s>
<s>
Snapshots	B-Application
require	O
only	O
the	O
"	O
delta	O
"	O
capacity	O
unless	O
created	O
with	O
full-provisioned	O
target	O
volumes	O
.	O
</s>
<s>
FlashCopy	B-Device
comes	O
in	O
three	O
flavours	O
:	O
Snapshot	B-Application
,	O
Backup	O
volume	O
,	O
and	O
Clone	O
,	O
which	O
is	O
automatically	O
unlinked	O
from	O
its	O
source	O
.	O
</s>
<s>
All	O
are	O
based	O
on	O
optimized	O
copy-on-write	B-Language
technology	O
.	O
</s>
<s>
Copy-on-write	B-Language
is	O
based	O
on	O
a	O
bitmap	B-Data_Structure
with	O
a	O
configurable	O
grain	O
size	O
,	O
as	O
opposed	O
to	O
a	O
journal	B-General_Concept
.	O
</s>
<s>
Rollback	O
requires	O
a	O
FlashCopy	B-Device
license	O
and	O
the	O
Spectrum	O
Control	O
Snapshot	B-Application
software	O
.	O
</s>
<s>
This	O
allows	O
a	O
remote	O
disaster	B-General_Concept
recovery	I-General_Concept
site	O
at	O
a	O
distance	O
of	O
thousands	O
of	O
kilometres	O
.	O
</s>
<s>
Each	O
Global	B-Application
Mirror	I-Application
relationship	O
can	O
be	O
configured	O
for	O
high	O
latency	O
/	O
low	O
bandwidth	O
or	O
for	O
high	O
latency	O
/	O
high	O
bandwidth	O
connectivity	O
,	O
the	O
latter	O
allowing	O
a	O
consistent	O
recovery	O
point	O
objective	O
RPO	O
below	O
1	O
sec	O
.	O
</s>
<s>
On	O
7	O
October	O
2010	O
,	O
IBM	O
announced	O
the	O
IBM	B-Device
Storwize	I-Device
V7000	I-Device
,	O
the	O
first	O
member	O
of	O
the	O
Storwize	B-Device
family	I-Device
.	O
</s>
<s>
Storwize	B-Device
uses	O
the	O
SAN	O
Volume	O
Controller	O
code	O
base	O
with	O
internal	O
storage	O
to	O
provide	O
a	O
mid-price	O
storage	O
subsystem	O
.	O
</s>
<s>
The	O
IBM	B-Device
Storwize	I-Device
V5000	O
,	O
V3700	O
and	O
V3500	O
are	O
shrunk	O
compatible	O
models	O
with	O
less	O
cache/CPU/adapters	O
and	O
a	O
reduced	O
set	O
of	O
features	O
.	O
</s>
<s>
The	O
IBM	B-Device
FlashSystem	I-Device
V9000	O
leverages	O
the	O
SVC	O
firmware	O
integrated	O
with	O
IBM	B-Device
FlashSystem	I-Device
solid-state	O
drawers	O
.	O
</s>
<s>
The	O
PAS	O
platform	O
spans	O
backup	O
,	O
disaster	B-General_Concept
recovery	I-General_Concept
,	O
and	O
business	O
continuity	O
among	O
other	O
functions	O
.	O
</s>
