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2.3 – Identify migration options

  • Cold migrations: move powered-off or suspended VM’s between hosts or datastores
  • hot migrations: move powered-on VM’s between hosts or datastores
  • Cross-host migrations: allows you to initiate cross-host migrations where you can choose the destination host, DRS cluster, resource pool or vAPP.
  • Cross-datastore migrations: moving VM’s to a new datastore
  • Cross vCenter migrations: moving VM’s from one vCenter to another vCenter

There are some limitations to VM migrations which you need to be aware of:

  • Network limits: Each vMotion receives a cost of 1 and on a 1GB NIC the limit is 4 and on 10GB NIC the limit is 8
  • Datastore limits: Each storage migration costs 16 and the limit datastores puts up is 128
  • Host limits: Provisioning and vMotion operations have a host cost of 1 and storage vMotion a host cost of 4. The host limit is 8

There are also some specific storage vMotion limitations:

  • Not supported during VMware tools installation
  • Disks larger than 2TB cant be migrated from VMFS 5 to VMFS 3
  • The source host must have a license that includes Storage vMotion
  • ESXI4 and later do not require specific vMotion configuration
  • The host where the VM is running on must have access to both the source and target datastores.

During an instant clone (vmFork) operation the system quiesces and stuns the source VM, creates and transfers a checkpoint, customizes the destination MAC address and UUID, and forks the memory and disk. The destination VM then shares the parent virtual machine’s disk and memory for reads. For writes, the destination VM uses copy on write (COW) to direct disk and memory changes to delta files and private memory space.

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