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hardware and software features that can provide that control and ensure the
most appropriate use of the available resources.
Non-uniform memory addressing (NUMA)
NUMA is a scalability technology for splitting servers with numerous processors
(CPUs) and large amounts of memory into resource groups, or NUMA nodes.
The processors in a NUMA node work primarily with the local memory in that
NUMA node while still having access to memory in other NUMA nodes (remote
memory). Using local memory is quicker than remote memory because of the
configuration of the NUMA node.
Because SQL Server 2005 is NUMA-aware, it tries to write data to physical
memory that is associated with the requesting CPU to benefit from the better
local memory access performance. If the requesting CPU does not have enough
memory available, it is allocated from another NUMA node.
Soft-NUMA, CPU affinity, and I/O affinity
Soft-NUMA is a SQL Server 2005 feature that you can use to group CPUs and
network interfaces into soft-NUMA nodes. However, you cannot allocate memory
to a soft-NUMA node and all memory requests are served from all memory
available to SQL Server.
To group CPUs, you must edit the registry directly using a node configuration
affinity mask. After the soft-NUMA nodes have been created, you can assign
individual SQL Server instances to one or more soft-NUMA nodes.
You might create soft-NUMA nodes if your server hardware does not have
hardware NUMA capabilities or to sub-divide a NUMA node further. Each
soft-NUMA node gets its own I/O thread and lazy writer thread. If the SQL
instance has a high I/O requirement, it could be assigned two soft-NUMA nodes.
The SQL instance then has two I/O threads that can help it process I/O requests
better. Soft-NUMA provides the ability to fine-tune the use of the server
resources to ensure that critical databases get the resources that they require
within a consolidated environment.
CPU affinity and I/O affinity are SQL Server 2005 features for configuring each
database instance to use specific CPUs for database processing and I/O
requests. Assigning a set of CPUs only to handle I/O processing might provide
performance benefits with a database that relies heavily on I/O operations.
Designating a certain number of CPUs to a critical database ensures that
performance is not affected by other processes running on the same server
because those processes are run on other CPUs in the server. CPU and I/O
affinity are used for fine-tuning the allocation of server resources to where they
are most required.
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Planning, Installing, and Managing the IBM System x3950 M2
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