问题描述：生产环境一个数据库从SQLSERVER 2008 R2升级到SQLSERVER 2012 ，同时更换硬件，但迁移后发现性能明显下降，应用写入、读取性能下降的比较厉害；
向微软寻求帮助后得出答案，原来这与SQLSERVER的安装介质有关。
大致意思是说由于NUMA架构可以自行管理内存池，在安装了CAL的EE后，由于限制只能使用20个cores，同样内存则只能管理到20个cores涉及到的NUMA的对应的内存空间（具体算法为 限制内存=当前物理内存/NUMA数量*(总核数/20)），如果限制SQL Server的最大使用内存超过前面说的限制内存，则当使用内存大于限制内存需要再向操作系统再申请空间时，则会产生跨NUMA处理的情况，导致大量消耗系统资源，引起性能下降；
http://blogs.msdn.com/b/saponsqlserver/archive/2012/06/15/sql-server-2012-enterprise-editions.aspx
这是我在网上找到的解释，摘录其中几段（本人E文水平有限，翻译不当之处敬请见谅）
关于SQLSERVER EE的安装介质（EE为Enterprise Editions简拼，企业版）
- SQL Server EE is no longer being offered under the Server + CAL (Client Access License) licensing model. For customers with Software Assurance on existing SQL EE Server licenses (or access to them under their current Enterprise Agreements during term) a version of Enterprise Edition was created to enable them to upgrade to SQL Server 2012. This version has technical restrictions limiting an instance to using only 20 processor cores (40 CPU threads with Hyperthreading).. Customers must still have the proper version of the CAL and additional physical and virtual use right restrictions of this SKU (Stock Keeping Unit) apply. Please refer to the three documents listed above for additional details.
- An Enterprise Edition which is licensed per core and which does not have limits on the # of cores usable on a server (within the absolute limits supported). This Enterprise Edition does reflect the new licensing model for SQL Server Enterprise Edition.
上面说到 即便是SQLSERVER EE，由于授权方式的差异导致对processor cores的限制
For customers with Software Assurance on existing SQL EE Server licenses
An Enterprise Edition which is licensed per core and which does not have limits on the # of cores usable on a server
通过以下方式可以检查当前运行的SQL EE信息
1、sp_readerrorlog ，第一行显示SQLSERVER 版本信息如下
2012-05-08 16:04:54.56 Server Microsoft SQL Server 2012 - 11.0.2100.60 (X64)
Feb 10 2012 19:39:15
Copyright (c) Microsoft Corporation
Enterprise Edition (64-bit) on Windows NT 6.1 <X64> (Build 7601: Service Pack 1)
2、select serverproperty('Edition') ，显示版本信息如下
Enterprise Edition (64-bit)
如何判断当前的SQL EE是基于per CAL还是per core的呢？如果显示的信息如上所示，那就是基于per CAL的，文中再次强调此模式下受限于20 cores；
Answer is: It is the CAL licensed one and with that the Enterprise Edition which is limited to 20 cores!!!
而如果显示的信息如下所示，那就是基于per core的 则没有限制；
The per-core licensed Enterprise Edition will show like this:
2012-05-18 23:57:29.77 Server Microsoft SQL Server 2012 - 11.0.2100.60 (X64)
Feb 10 2012 19:39:15
Copyright (c) Microsoft Corporation
Enterprise Edition: Core-based Licensing (64-bit) on Windows NT 6.1 <X64> (Build 7601: Service Pack 1)
Executing:
select serverproperty('Edition')
which then could show this result:
Enterprise Edition: Core-based Licensing (64-bit)
关于20 cores的限制问题，需要区分CPU是否支持超线程而言
Other indications that there might be a limitation to 20 cores could be identified as well at the beginning of the SQL Server 2012 errorlog where we can find a message like:
SQL Server detected 4 sockets with 6 cores per socket and 6 logical processors per socket, 24 total logical processors; using 20 logical processors based on SQL Server licensing.
In the case above, we are looking at a server with the last generation of Intel processors which did not have Hyperthreading yet. Or in more modern Intel Servers with Hyperthreading it would look like:
SQL Server detected 4 sockets with 8 cores per socket and 16 logical processors per socket, 64 total logical processors; using 40 logical processors based on SQL Server licensing.
上文中的描述，根据SQL Server 2012 errorlog中的内容，我们可以看到
如果SQL Server 检测到 4个插槽，每个插槽有6个核，且有6个逻辑处理器（单线程），则总共为24个逻辑处理器，受限于SQL Server licenseing，只能使用20个逻辑处理器；
对于超线程CPU：
如果SQL Server 检测到 4个插槽，每个插槽有8个核，且有16个逻辑处理器（单线程），则总共为64个逻辑处理器，受限于SQL Server licenseing，只能使用40个逻辑处理器；
Another possibility of discovery is through the Microsoft MAP toolkit. Where to get it and how to use it is excellently described in this document: http://download.microsoft.com/download/F/F/2/FF29F6CC-9C5E-4E6D-85C6-F8078B014E9F/Determining_SQL_Server_2012_Core_Licensing_Requirements_at_SA_Renewal_Apr2012.pdf
另外一种可能的发现是通过Microsoft MAP toolkit，可以在以下这个文档中得到更准确的描述；
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How is the throttle of 20 cores enforced for the CAL license-based Enterprise Edition?
The limitation or the cap is enforced by the # of SQL Server schedulers. Usually SQL Server creates one scheduler thread for every logical CPU on a server. Each of those scheduler threads is administrating a pool of worker threads which execute requests or are in different other states. A scheduler only can have one thread running at maximum. If a scheduler thread over all of the time has one of worker threads running, it can leverage at maximum one logical CPU and not a bit more. If there are (as in the second situation above) only 40 schedulers active to schedule worker threads, the maximum number of CPU power we can use at any given time is 40 logical CPUs.
Querying sys.dm_os_schedulers with this query:
select * from sys.dm_os_schedulers
we will realize that the all the schedulers are ‘Visible’ for all the logical CPUs, but only 40 of them will be ‘Online’, whereas the others are ‘Offline’
If you disable Hyperthreading, the number of schedulers being Online will decline to 20, since one single core is now represented by one CPU thread only compared to two with Hyperthreading enabled. In cases where there are many more CPU threads or logical CPUs than the limit of the Server+CAL licensed SQL Server 2012 Enterprise Edition, one certainly can use affinity mask settings to chose the CPUs SQL Server shall use.
通过sys.dm_os_schedulers这个DMV可以查询到SQL Server调度线程的情况；
如何在EE的两个不同的产品间变更？在下面的链接中可以找到答案
http://msdn.microsoft.com/zh-cn/library/ms143393.aspx
