Database Reference
In-Depth Information
workloads.
Clock for Clock performance between CPU generations is important to compare when
evaluating a Single Compute Unit Performance comparison. Often between CPU
generations, the same clock speed can achieve up to 15% increase in performance.
Many SQL queries will benefit from a higher system clock speed, especially when they
are CPU intensive, single threaded, and long running. However, applications and
queries that are generally very parallel in nature and combine lots of small execution
payloads will run just fine on a system with a lower clock speed but many processors.
The Max Degree of Parallelism setting on your SQL Server database is one setting that
will impact the degree of parallelism for your SQL queries, in addition to the individual
query execution plan. It is recommended this parameter be set equal to 1 for OLTP
workloads and only changed from 1 if testing shows a benefit. The tradeoff when
increasing this value is that one user or one connection could monopolize the resources
of the database.
Blended Peaks of Multiple Systems
When you virtualize multiple systems, you will most likely be consolidating them onto a
fewer number of physical servers. Although there are cases where customers choose to
consolidate 1:1, this is by no means the norm. As a result of this, you need to ensure that
the peaks of all of the systems that will be running on a particular host combined do not
exceed the resources of that host. This is something you should be capturing during your
baselining, benchmarking, and validation of the virtual infrastructure.
If all of your virtualized SQL Server databases have log shipping, backup, or
maintenance tasks scheduled to run at exactly the same time, this may reduce the
consolidation ratios that are possible. Failure to consider blended peak workloads of
multiple systems per host could result in your databases not meeting their SLAs during
peak times. If you get your estimates slightly wrong and there is spare capacity within
your clusters, VMware DRS will load-balance VMs across the cluster automatically. It
is recommended that you have DRS enabled and set to fully automatic. Figure 10.3
shows a blended workload of an OLTP database and a batch-driven data warehouse-
type database virtualized on the same host to demonstrate how two different workloads
can coexist happily and improve overall utilization.
 
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