Configuring HP SIM for Optimal Performance in Large Environments
22
Previously with Windows Server 2003 x32, system memory was divided; 2GB was allocated to user-
mode processes and 2GB to kernel-mode process address space. If allocating more memory to user-
mode space was desired, the /3gb switch could be placed in the boot.ini file. With Server 2008, the
IncreaseUserVA boot option can be used to increase user-mode address space, thus making more
memory available to user processes. This setting is applied using the bcdedit tool as follows:
>Bcdedit /set IncreaseUserVA 3072
Configuring
Microsoft
Windows
Server
2008
x32
to
use
PAE
Microsoft
Windows
Server
2008
does
not
support
setting
boot
options
in
the
boot.ini
file.
Instead, you
must
employ
the
BCDEdit
utility
to
configure
PAE
options.
(The
PAE
option
applies
only
to
32-bit
Windows
versions.)
If
the
system
is
configured
for
hot-add
memory
devices
with
address
ranges
beyond
4
GB,
Windows
Server
2008
automatically
configures
itself
with
the
PAE
option
enabled.
To
enable
PAE,
enter
the
following
command:
>bcdedit
/set
{current}
pae
default
(or
ForceEnable)
Before
configuring
PAE
in
Microsoft
Windows
Server
2008,
consult
the
BCDEdit
reference
page
at:
http://msdn.microsoft.com/en-us/library/aa906211.aspx.
Using
AWE
memory
in
Microsoft
SQL
Server
2008 x32
to
access
more
than
2
GB
memory
AWE
is
not
needed
and
cannot
be
configured
on
64-bit
operating
systems.
Though
the
Use
AWE
option
is
available
in
Microsoft
SQL
Server
2008
64-bit
edition,
it
is
ignored.
However,
it
is
still
recommended
that
this
option
be
selected.
Because
many
Microsoft
SQL
Server
databases
are
huge,
greatly
exceeding
2
GB,
more
than
2
GB of
RAM
is
often
needed
to
attain
a
90%
or
greater
buffer
cache
ratio.
Because
of
this
problem, Microsoft
Windows
Server
2008
and
Microsoft
SQL
Server
2008
support
a
feature
called
Address Windowing
Extensions
(AWE).
AWE
is
a
way
to
allow
Microsoft
SQL
Server
2008 x32
to
access
more than
2
GB
of
memory.
In
most
Microsoft
SQL
Servers,
the
biggest
performance
bottleneck
is
input/output.
First,
the
purpose of
a
database
is
to
store
data,
and
data
is
stored
on
disk
arrays,
requiring
input/output
to
retrieve
the
data
from
the
disk
array
before
it
can
be
put
into
RAM
for
use.
Second,
disk
access
is
the
slowest
component
of
any
Microsoft
SQL
Server.
Combined,
these
two
factors
contribute
to
this
common
bottleneck.
To
help
reduce
input/output
bottlenecks,
Microsoft
SQL
Server
includes
a
buffer
cache,
located
in
RAM,
used
to
store
the
most
recently
accessed
Microsoft
SQL
Server
data.
By
caching
data,
Microsoft
SQL
Server
does
not
need
to
access
disk
input/output
as
often,
helping
to
boost
overall
performance of
Microsoft
SQL
Server.
The
greater
the
size
of
the
buffer
cache,
the
more
data
Microsoft
SQL
Server
can
store
in
RAM,
and the
less
input/output
access
is
required.
In
an
ideal
world,
all
of
the
data
in
a
database
would
be stored
in
the
buffer
cache,
greatly
reducing
disk
input/output,
and
boosting
Microsoft
SQL
Server's performance.
In
some
cases,
this
is
possible,
but
in
most
cases,
it
is
not.
For
ideal
performance,
the
buffer
cache
hit
ratio
(the
amount
of
data
in
RAM
that
is
being
reused)
should
exceed
90%.
If
it
does,
excessive
disk
input/output
is
generally
avoided,
helping
performance.
But
if
the
buffer
cache
hit
ratio
is
less
than
90%,
then
disk
input/output
might
become
a
serious
bottleneck.
The
easiest
way
to
boost
the
buffer
cache
hit
ratio
in
a
Microsoft
SQL
Server
is
to
allocate
additional
physical
RAM
to
the
Microsoft
SQL
Server.
Assuming
you
have
not
changed
the
default
memory
configuration
settings
in
Microsoft
SQL
Server
it
then
automatically
uses
as
much
RAM
as
you
add
to
your
server.