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VSICM51 - Slide 07-31 - Migrating Virtual Machines



1. Wrong:

In the slide graphic, last bullet states:

A maximum of eight simultaneous vMotion, cloning, deployment, or Storage vMotion accesses to a single VMware vSphere® VMFS-5 datastore is supported.
1. Correct:

Starting with vSphere 4.1, the maximum number of simultaneous vMotion operations per datastore has been increased to 128. Additionally there is no difference, in terms of maximum concurrent operations, between a VMFS-3, a VMFS-5 or an NFS datastore. Other limits listed in the slide - cloning, deployment and Storage vMotion - are still valid as of vSphere 5.1.

1. Info:

More details about why the above limits apply to datastores and hosts can be found in the "vCenter Server and Host Management" guide, "Migrating Virtual Machines in the vSphere Client" chapter - "Limits on Simultaneous Migrations" paragraph, available in the vSphere 5.1 Documentation Center.

1. Source:

Configuration Maximums for VMware vSphere 4.1.

Configuration Maximums for VMware vSphere 5.0.

Configuration Maximums for VMware vSphere 5.1.



2. Wrong:

At the end of the slide notes you can read that:

With file relocation, the contents of the raw LUN mapped by the RDM are copied into a new .vmdk file at the destination. The copy operation is effectively converting a raw LUN into a virtual disk.
If you must cold-migrate a virtual machine without cloning or converting its RDMs, remove them from the configuration of the virtual machine before migrating and re-create them when migration has completed.
2. Correct:

This was a typical behavior for RDMs in vSphere 4.x, yet in vSphere 5.x it has been improved.
Cormac Hogan - a senior technical marketing architect within the Cloud Infrastructure Product Marketing group at VMware - has further clarified RDM behavior during Storage vMotion operations.

  • VM with Physical (Pass-Thru) RDMs (Powered On – Storage vMotion):
    • If I try to change the format to thin or thick, then no Storage vMotion allowed.
    • If I chose not to do any conversion, only the pRDM mapping file is moved from the source VMFS datastore to the destination VMFS datastore – the data stays on the original LUN.
  • VM with Virtual (non Pass-Thru) RDMs (Power On – Storage vMotion):
    • On a migrate, if I chose to covert the format in the advanced view, the vRDM is converted to a VMDK on the destination VMFS datastore.
    • If I chose not to do any conversion, only the vRDM mapping file is moved from the source VMFS datastore to the destination VMFS datastore – the data stays on the original LUN (same behavior as pRDM).
  • VM with Physical (Pass-Thru) RDMs (Powered Off – Cold Migration):
    • On a migrate, if I chose to change the format (via the advanced view), the pRDM is converted to a VMDK on the destination VMFS datastore.
    • If I chose not to do any conversion, only the pRDM mapping file is moved from the source VMFS datastore to the destination VMFS datastore – the data stays on the original LUN.
  • VM with Virtual (non Pass-Thru) RDMs (Power Off – Cold Migration):
    • On a migrate, if I chose to covert the format in the advanced view, the vRDM is converted to a VMDK on the destination VMFS datastore.
    • If I chose not to do any conversion, only the vRDM mapping file is moved from the source VMFS datastore to the destination VMFS datastore – the data stays on the original LUN (same behaviour as pRDM).
2. Source:

VMware vSphere Blog.


Last modified onThursday, 12 December 2013 19:25
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