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Requirements for Creating Resource Pools

Jun 14, 2017
Requirements for Creating Resource Pools
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A resource pool is a homogeneous (or heterogeneous with restrictions, see the section called “Creating Heterogeneous Resource Pools”) aggregate of one or more XenServer hosts, up to a maximum of 16. The definition of homogeneous is:

  • the CPUs on the server joining the pool are the same (in terms of vendor, model, and features) as the CPUs on servers already in the pool.

  • the server joining the pool is running the same version of XenServer software, at the same patch level, as servers already in the pool

The software will enforce additional constraints when joining a server to a pool – in particular:

  • it is not a member of an existing resource pool

  • it has no shared storage configured

  • there are no running or suspended VMs on the XenServer host which is joining

  • there are no active operations on the VMs in progress, such as one shutting down

You must also check that the clock of the host joining the pool is synchronized to the same time as the pool master (for example, by using NTP), that its management interface is not bonded (you can configure this once the host has successfully joined the pool), and that its management IP address is static (either configured on the host itself or by using an appropriate configuration on your DHCP server).

XenServer hosts in resource pools may contain different numbers of physical network interfaces and have local storage repositories of varying size. In practice, it is often difficult to obtain multiple servers with the exact same CPUs, and so minor variations are permitted. If you are sure that it is acceptable in your environment for hosts with varying CPUs to be part of the same resource pool, then the pool joining operation can be forced by passing a --force parameter.

Note

The requirement for a XenServer host to have a static IP address to be part of a resource pool also applies to servers providing shared NFS or iSCSI storage for the pool.

Although not a strict technical requirement for creating a resource pool, the advantages of pools (for example, the ability to dynamically choose on which XenServer host to run a VM and to dynamically move a VM between XenServer hosts) are only available if the pool has one or more shared storage repositories. If possible, postpone creating a pool of XenServer hosts until shared storage is available. Once shared storage has been added, Citrix recommends that you move existing VMs whose disks are in local storage into shared storage. This can be done using the xe vm-copy command or XenCenter.


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