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Re: [Xen-API] Difference between Affinity and residenton filed of VMs

To: Gandhiraj Natarajan <gandhiraj_gk@xxxxxxxxxxx>
Subject: Re: [Xen-API] Difference between Affinity and residenton filed of VMs
From: Jonathan Knowles <jonathan.knowles@xxxxxxxxxxxxx>
Date: Thu, 10 Dec 2009 09:57:28 +0000
Cc: XenAPI <xen-api@xxxxxxxxxxxxxxxxxxx>
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Hi Gandhiraj

Gandhiraj Natarajan wrote:
What is the difference between affinity and residentOn filed of VMs in pool?

A VM's affinity host is its "preferred" host.

XenServer interprets the "affinity" field as a preference
for where to start/resume a VM for start/resume operations
that don't specify a particular host.

If you don't specify a particular host when starting a VM,
then XenServer considers the affinity host first, and will
start the VM on that host provided it is suitable. It must:

  * have enough memory
  * be able to access all SRs required by the VM.

If the affinity host is unsuitable for any reason, then
XenServer will attempt to start the VM on another host
that is suitable.

XenServer ignores the "affinity" field for /start-on/ and
/resume-on/ operations that /do/ specify a particular host.

XenServer only populates the "resident-on" field once you
start a VM. It points to the actual host on which the VM
is currently running.

Hope this helps :)


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