Getting started with Flash Accel : Preparing for vMotion migration

Preparing for vMotion migration
VMware vMotion enables live migration of running virtual machines from one physical server to another. You migrate a cached VM with vMotion the same way you migrate any VM. The migration policy you specify ensures that there is enough cache space available on each potential migration target.
A migration policy specifies whether you want to enable vMotion migration for Flash Accel-enabled VMs, and the migration scope: the potential target hosts for cached VMs. You might target all the hosts in a cluster, for example, or all the hosts in a datacenter.
After you select a migration policy, the amount of cache space you can allocate to a VM is limited not only by the cache space available on its host, but also by the cache space available on each migration target. So if the VM resides on host X, with 100 GB of unallocated cache, and host Y and host Z are both potential migration targets, with 75 GB and 50 GB of unallocated cache, respectively, the maximum cache space you can allocate to the VM is 50 GB. If you allocate 50 GB of cache to the VM, you will see the Cache Used field for all three hosts increase by 50 GB.
The key point to remember about the migration policy is that the availability of cache space on hosts is determined at the time of cache allocation. Changing the policy after cache allocation will not free cache space on hosts. Similarly, adding a host to a cluster or datacenter after cache allocation will not reserve cache on that host.
After cache allocation, you can override the migration policy for a given VM by clicking the wrench icon for the VM and selecting Advanced > Migration. Even then, the cache allocation for the VM remains the same until you change it explicitly.
Note: Use a shared datastore, accessible to each potential migration target host, to store the RDMP file for the Flash Accel pRDM device.
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Selecting a migration policy
Overriding the migration policy
Parent Topic: Getting started with Flash Accel
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