timarbour
Contributor
Contributor

Vmware is NOT hardware independent

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I have 2 Vmware ESXi Servers - An intel based server and an AMD based server. Purchased Essentials Plus because I wanted to have VCenter to migrate and clone from one server to the other. This cannot be done. I call support and was also told it could not be done as CPU types DO matter.

Now I'm really concerned about Disaster Recovery. I am backing up my entire VMs for DSR and if I go to restore at my DSR site, I'm not always guaranteed what I will get (Intel or AMD). I have been able to bare-metal restore machines but they do take time.

Any suggestions? How do others handle this issue? (I think Vmware needs to STOP selling their virtualization products as "hardware independent" as it's NOT true)

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devzero
Expert
Expert

>The claim is that virtual machines are independent of the host hardware, and that is a correct statement.

If you build a VM on one host with one type of hardware, you can (all things being configured equally -

>network connectivity, storage, etc) run that virtual machine on any hardware.

that`s not entirely true.

one may have

1. an operating system with a kernel optimized/built for a specific cpu type

2. programs optimized/built for a specific cpu type

3. software using a special license technology which gathers information from cpu to detect if it`s being relocated to other hardware

these are special cases, but it may bring you into trouble when you relocate such a vm.

at least i have seen case 1 and 3 in real life

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bulletprooffool
Champion
Champion

Unfortunately you are partly right, It is not possible to vMotion a VM from an intel Host to an AMD Host.

You could however cold vMotion a VM fro mone to the other - unfortunately yht eprocessor arvchitectures are so different that if you were able to mask the difference between the processors, you'd have to run the VM on practically NO instructions,

Look into EVC to understand what masking is, but you will not find a way to hot migrate your VMs

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=100321...

One day I will virtualise myself . . .
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devzero
Expert
Expert

why should clone or cold-migrate not work?

ok, no vmotion as this is somewhat "sticky" to the cpu - but moving a VM from a host with intel cpu to amd and vice versa ?

i did not try that, but i wonder what`s the problem with that....

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jjkrueger
VMware Employee
VMware Employee

VMware has never claimed that ESX is hardware independent - as a matter of fact, there is an explicit listing of compatible hardware in the Compatibility Guides. The claim is that virtual machines are independent of the host hardware, and that is a correct statement. If you build a VM on one host with one type of hardware, you can (all things being configured equally - network connectivity, storage, etc) run that virtual machine on any hardware.

That said, CPU type, in particular, is important. But it's only important for live migration/cloning activities. This is due to the nature of the operating systems we run in virtual machines. Windows, for example, probes the CPU during boot with a CPUID command. When Windows gets the result for this query, it loads a driver appropriate for the CPU's capabilities. ESX passes that command straight to the CPU, and hands the response directly into the virtual machine. As such, the guest OS in the VM knows that CPU is in the hardware, and takes advantage of its particular feature set. Imagine what would happen to the guest if that instruction set changed on the fly? I see a kernel panic in the immediate future of such an event.

EVC (Enhanced VMotion Compatibility) was mentioned, but that won't do any good between Intel and AMD hosts. What EVC does is essentially sets a global CPUID mask for a DRS-enabled cluster, and presents that CPUID mask to all VMs in the cluster. This does ease the concern for identical CPUs, but doesn't completely alleviate it. There is a requirement for all-Intel or all-AMD hosts in the DRS cluster with EVC turned on.

Migrations and cloning can be done between an Intel host and an AMD host, but the source VM must be powered off for these operations to function. From how you describe your setup, I don't know that this is an issue. When you recover your VMs at your DR site, they should be in a powered-off state. This should allow you to power them back on with no issues - the guest will pick up the new CPU and work accordingly.

What you're seeing isn't so much a problem with virtualization, but rather a problem with the design of Operating Systems. We just never had the opportunity to see the problem in traditional, hardware-based installations, as the OS was absolutely tied to a specific piece of hardware. With virtualization, that's no longer the case, and these kinds of design decisions begin to form significant challenges.

Hope that makes sense,

-jk

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anupama
Contributor
Contributor

Have a look on this... You can get better understanding..

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AndreTheGiant
Immortal
Immortal

why should clone or cold-migrate not work?

It works.

A powered off VM is hardware independent!

It depends only by the virtual hardware version.

But a powered on VM has a CPU state that depends by the type of CPU... this is the reason that you need compatible CPU to do a VMotion.

EVC can help, but CPU must be in the same "family".

Note that this problem is the same also in other virtualization products: a live migration require compatible CPU.

Andre

Andre | http://about.me/amauro | http://vinfrastructure.it/ | @Andrea_Mauro
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AntonVZhbankov
Immortal
Immortal

>>why should clone or cold-migrate not work?

>It works.

Moreover, I successfully VMotioned a couple of VMs between Xeons and Opterons. Yes, that is not supported, not recommended etc, but it can be performed in some cases.


---

VMware vExpert '2009

http://blog.vadmin.ru

EMCCAe, MCITP: SA+VA, VCP 3/4/5, VMware vExpert http://blog.vadmin.ru
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devzero
Expert
Expert

>The claim is that virtual machines are independent of the host hardware, and that is a correct statement.

If you build a VM on one host with one type of hardware, you can (all things being configured equally -

>network connectivity, storage, etc) run that virtual machine on any hardware.

that`s not entirely true.

one may have

1. an operating system with a kernel optimized/built for a specific cpu type

2. programs optimized/built for a specific cpu type

3. software using a special license technology which gathers information from cpu to detect if it`s being relocated to other hardware

these are special cases, but it may bring you into trouble when you relocate such a vm.

at least i have seen case 1 and 3 in real life

View solution in original post

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PhallusaurusRex
Contributor
Contributor

what about moving from one intel cpu to another? say core2duo to xeon

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RParker
Immortal
Immortal

what about moving from one intel cpu to another? say core2duo to xeon

Cold cloning ALL Intel CPU are compatibile, there is only a problem between AMD and Intel, and it's usually in one direction, FROM Intel to AMD the AMD will have issues, but going from AMD TO Intel isn't much of an issue.

Intel CPU all work together fine. You may not be able to vmotion.. but you can always migrate / clone.

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