pearlyshells
Contributor
Contributor

I understand that VMs can not be vmotioned to other hosts unless they exist on the same LUN.....but, since the hosts don't reside on LUNs I don't understand this concept. When I want to vmotion a VM it is going from one host to another....not LUNs. What am I missing?

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admin
Immortal
Immortal

This is a marketing document but it explain vMotion basic

http://www.vmware.com/pdf/vmotion_datasheet.pdf

View solution in original post

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esiebert7625
Immortal
Immortal

Vmotion requires shared storage that all ESX servers can see (SAN, iSCSI, NFS). If you use local disk storage you cannot use Vmotion. So when you Vmotion a VM from one server to another none of the files are actually being moved from one ESX host to another the VM is simply being re-located in memory from one ESX host to another.

Vmotion requirements - http://www.vmware.com/pdf/vi3_admin_guide.pdf (Chapter 14)

spex
Expert
Expert

LUNs are shared between ESX hosts. During vmotion only active RAM of the vm is copied to the target host. When RAM is in sync IO (and all cpu) activity is done by the new esx host still to the same lun.

Regards Spex

admin
Immortal
Immortal

This is a marketing document but it explain vMotion basic

http://www.vmware.com/pdf/vmotion_datasheet.pdf

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oreeh
Immortal
Immortal

Basically vMotion transfers the VMs memory and CPU state from one ESX to another.

Disk files are (normally) too big to transfer them to another host without interrupting the VM - which would make vMotion useless - therefore

the need for a shared storage.

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acr
Champion
Champion

As stated a prereq for VMotion, DRS and HA is shared storage...

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pearlyshells
Contributor
Contributor

thanks very much to everyone. So, I understand now. As long as all the Hosts have access to the same Lun or Lun's, moving VMs with their files located on a shared LUN can be moved between the hosts since the VM files remain in the same LUN location. The VM is hosted on a different Virtual host server but its files are still in the same location.

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esiebert7625
Immortal
Immortal

Exactly.

fyi....don't forget to award points for helpful answers using the Helpful/Correct buttons....thanks

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pearlyshells
Contributor
Contributor

many thanks.....will do

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