Microsoft® SQL Server® 2012 Bible

489

Chapter 19: Confi guring SQL Server

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FIGURE 19-7

The Processors tab shows the processors available on the system and enables you to set how

SQL Server uses them.

SQL Server supports processor affi nity by means of two affi nity mask confi guration options:

affinity mask (also referred to as CPU affi nity mask) and affinity I/O mask. The

affinity mask confi guration option enables you to specify which CPUs on a multiprocessor

computer are to be used to run threads from SQL Server. The affinity I/O mask confi gura-

tion option enables you to specify which CPUs are confi gured to run SQL Server threads related

to I/O operations. These two confi guration options give you the ability to allocate particular

CPUs for disk IO processing and particular CPUs for nondisk-related CPU requirements.

The affi nity mask is a bitmap in which the rightmost bit specifi es the lowest-order CPU(0), the

next rightmost bit specifi es the next lowest-order CPU(1), and so on. A 1-byte (8 bits) mask

covers 8 CPUs in a multiprocessor server, a 2-byte mask covers up to 16 CPUs, a 3-byte mask

covers up to 24 CPUs, and a 4-byte mask covers up to 32 CPUs. A 1 bit specifi es that the corre-

sponding CPU is allocated and a 0 bit specifi es that the corresponding CPU is not allocated.

When you confi gure the affi nity mask option, you must use it with an affi nity I/O mask.

Enabling the same CPU for both affi nity mask and affi nity I/O mask confi guration options

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