HP ProLiant DL980 G7 Server - Manual (Page 26)

processors (thereby reducing context switching). Such an association between a thread and a
processor is called processor affinity.
HP ESO generally recommends that you confine SQL instances with relatively light workloads to
under-utilized CPUs. This results in some SQL instance affinities being assigned an unusually high
order, or non-contiguous logical CPU number. Similarly, SQL Server and the operating system
automatically manage the CPU affinities of highly-utilized SQL instances. This logic results in less
conflict over CPU resources among under- and highly-utilized SQL instances.
Figure 27 CPU Page
SQL Server Affinity
On multi-processor systems, SQL Server interaction with CPU resources can be controlled by setting
the affinity mask options. Configuring these options results in SQL Server threads being scheduled
to run on the same processor each time they run. If you do not configure these options, the threads
can migrate among processors. In SQL Server 2008 R2 you can set SQL Server Affinity to a
maximum of 256 CPUs. In older versions of SQL Server this setting is limited to only 64 CPUs.
IO Affinity
The IO Affinity option binds SQL Server disk I/O to a specified subset of CPUs. In high-end SQL
Server online transactional processing (OLTP) environments, this extension can enhance the
performance of SQL Server threads issuing I/Os. This enhancement does not support hardware
affinity for individual disks or disk controllers.
NOTE: Do not set SQL Server Affinity and IO Affinity to the same CPUs because it can degrade
system performance (HP ESO displays a warning if the system is configured this way). As a general
rule, HP ESO recommends affinity on only a few specific processors for SQL instances that are
comparatively lightly utilized, so they do not use all of the available system processors. Likewise,
HP ESO does not recommend CPU Affinity for heavily utilized SQL instances, so they can use all
of the available system processors.
Storage
The Storage page displays recommendations for different storage parameters.
26 Using HP ESO