【连载】vSphere 4.0 问答(4) --- vCenter服务器可以是台VM么？

问：vCenter服务器可以是台虚机么？
答：为啥不能？当然能！只要给这台虚机配置足够的资源。
即使vCenter服务器不可用，VMware环境（包括集群环境）仍然可以正常工作，不受影响。

坏处是，在一些不寻常的问题发生时（比如vCenter所在那台物理主机坏了），你将没有vCenter服务器来帮助诊断、解决问题。但是这不是不能克服的，你完全可以将vSphere client直接连接到Host来进行排错和管理。

因此，我们建议在任何情况下都安装虚拟的vCenter服务器。因为它将获得VM的高可用性(HA)以及轻松备份/恢复的能力。

但是，使用虚拟的vCenter服务器要注意以下事项：
1) vCenter VM要禁用DRS，并且要在文档中记录下vCenter是位于哪一台主机上（我们建议用集群中的第一台主机）
2) 要启用HA，并将启动优先级设置成高。
3) 要确保vCenter虚机获得足够的资源，将share设置成High，甚至设置一些reservation
4) 要确保vCenter虚机在断电后会自动启动( Configuration –> Virtual Machine Startup and Shutdown)
5) 要确保vCenter所依赖的重要服务/服务器具有高优先级，并会按一定顺序自动启动。如AD –> DNS –> SQL

如果你的vCenter用的数据库服务器也是虚机，那建议将vCenter服务器和数据库服务器做一个绑定(Affinity), 以保证这2台VM会呆在同一台主机上。这样可以将由此产生的网络流量控制在一台主机的范围内。

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Can my vCenter server be a Virtual Machine? 

There is no reason why your vCenter server can’t be a virtual machine as long as it meets the requirements and gets the resources it needs. The environment (and especially HA) will continue to function if the host where the vCenter server resides becomes unavailable. The drawback to doing this is that if there is an unusual problem (e.g., where your host that’s hosting vCenter is having issues, or where the VM is not easily recovered), you will not have your vCenter server to manage/troubleshoot the environment. Of course you can always use your vSphere Client directly connected to a host in these situations.

We recommend a virtual vCenter server in any environment as it will make your vCenter server instantly highly available and it eases disaster recovery as it can be cloned with just a few steps.

However, when virtualizing vCenter remember a couple of things:

1.     Disable DRS(Change Automation Level!) for your vCenter VM and make sure to document where the vCenter server is located (Our suggestion would be the first ESX host.)
2.     Enable HA for the vCenter server, and set the startup priority to high
3.     Make sure the vCenter server gets enough resources by setting the shares “high”, and maybe even set reservations
4.     Make sure vCenter starts up automatically when a power cut occurs (Configuration, Virtual Machine Startup and Shutdown)
5.     Make sure other services and servers that vCenter relies on are also starting automatically, with a high priority and in the correct order like:
       a.      Active Directory
       b.     DNS
       c.      SQL

If your vCenter database is also virtual, setting an affinity rule to keep both virtual machines on the same host will increase performance. All network traffic will remain inside the host.