In a production environment, it's often important to have some flexibility on its servers. For this, we will use the XenServer pools system.
Then, it's also important to provide the best possible availability. This is often possible by configuring high availability (HA) of the solution used.
In this complete tutorial, we will explain how to :
Create a server pool allows you to get some flexibility and a fault tolerance in case of one of your XenServer servers will fail or that you should put it in maintenance.
Indeed, with the pools, it's possible to run a virtual machine on the server of your choice.
However, to use this system, you need to use an external storage server (NAS, NFS, iSCSI, ...) that will be shared between the servers of the pool.
Why use servers pools ?
To get flexibility.
When you create a server pool :
What is the difference between homogeneous pool and heterogeneous pool ?
Homogeneous pool :
A homogeneous pool means that all XenServer servers of the pool must have identical hardware. Including the same processor model.
If this is not the case, the creation of homogeneous pool will not work.
In addition, homogeneous pool is recommended, especially to get the best performance that you can have with your hardware.
Heterogeneous pool :
A heterogeneous pool means that at least one pool of servers have a different hardware, or uses at least a different processor from those present in your other servers.
In this case, you can not create the pool without making changes beforehand.
In the case of heterogeneous pool, you will need to hide the features of one or more processors in order for they use the same functionality and are therefore compatible.
Which means that you may risk losing performance. However, that will work too.
Here is some important information from the "XenServer 6.5.0 Service Pack 1 Administrator's Guide" of Citrix.
The official documentation of Citrix XenServer 6.5.0 is available at : docs.vmd.citrix.com
Then you have also set static IP addresses on all of your servers :
Finally, for high availability (HA), Citrix recommends enabling the HA only if your pool contains at least 3 XenServer servers.
For this tutorial, we will use only 2 servers with high availability, but in production, it will be preferable to have at least 3 XenServer servers in your pool.
For this tutorial, we'll use :
* Our XenServer servers have two NICs each to ensure maximum compliance with the HA requirements specified in their official documentation.
Indeed, as you will see later, Citrix says in its documentation that you should always use linked network cards (which involves doubling their number) to use the high availability in the best conditions.
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