HyperV's Dynamic Memory in VMware - when?

[FredPeterson]

So if anyone has actually gotten a chance to take a look at what Dynamic Memory in Hyper-V actually is has to be thoroughly impressed.  Its actually an outstanding feature that, while differing in intent and functionality from VMwares memory technologies, it has immense potential for all types of workloads that grow over time, or spontaneously grow for short bursts.

So I was thinking, considering how Dynamic Memory works - the big question is - when is VMware going to implement it?  Unless Microsoft is keeping secret the deep API within Server 2008 and Windows 7, theres no reason why VMware cannot implement it.

[mcowger]

VMware is notoriously secret about futures.  Anyone that would know can't talk about it

[a_p_]

Maybe I'm overlooking something, but implementing Hyper-V's Dynamic Memory would IMHO be a downgrade of the already implemented memory management. With ESX(i) you have transparent page sharing, over-commitment, ballooning, memory compression and these options are supported in a lot more guest operating systems. Is there anything specific you are looking at with Dynamic Memory?

André

[FredPeterson]

André Pett wrote:

Maybe I'm overlooking something, but implementing Hyper-V's Dynamic Memory would IMHO be a downgrade of the already implemented memory management. With ESX(i) you have transparent page sharing, over-commitment, ballooning, memory compression and these options are supported in a lot more guest operating systems. Is there anything specific you are looking at with Dynamic Memory?

André

Can I turn it around and ask you if you've actually looked at what Dynamic Memory does and how it works?

Its all fine and dandy that the Hypervisor-only features you describe are supported by more operating systems (really only ballooning has connections to the OS), that doesn't negate what DM brings to the table for the future of Windows operating systems in a virtual environment.

DM is a complementary technology to the memory management techniques VMware has developed.

In my mind I see it as DM becoming the first line of "memory management", then its the more advanced Hypervisor only techniques that VMware brings to the table.  DM might prevent many of those technologies from being used though.

[Linjo]

It should be possible to implement "Dynamic Memory" with a small powershell script in vSphere4.

Just hot-add more memory to the vm whenever it consumed 95% of its memory, then let the ballon-driver take care of the rest, reset the memory whenever the VM is restarted.

Can't really see why anyone would do it since the existing memory technologies in vSphere are superior to that, but it would be fun todo anyway.

Maybe a weekend-project? 😉

// Linjo

[FredPeterson]

Joel Lindberg wrote:

It should be possible to implement "Dynamic Memory" with a small powershell script in vSphere4.

Just hot-add more memory to the vm whenever it consumed 95% of its memory, then let the ballon-driver take care of the rest, reset the memory whenever the VM is restarted.

Can't really see why anyone would do it since the existing memory technologies in vSphere are superior to that, but it would be fun todo anyway.

Maybe a weekend-project? 😉

// Linjo

Ah, but you mention the key evil word that DM doesn't need, plus your guest needs to be Enterprise or Datacenter to Hot Add.

[DSTAVERT]

I would agree with André. I think the only thing that DM would provide is the ability to underprovision RAM. As it is now for the most part I think we all overprovision RAM. VMware takes care of that overprovisioning. If we underprovision and let DM provide the busts of access what happens when we are truely overcommitted?

[FredPeterson]

David Stavert wrote:

I would agree with André. I think the only thing that DM would provide is the ability to underprovision RAM. As it is now for the most part I think we all overprovision RAM. VMware takes care of that overprovisioning. If we underprovision and let DM provide the busts of access what happens when we are truely overcommitted?

This assumes you don't pay any attention to your environment.

If a black swan event occurs and suddenly all of your servers use DM and over-commit the host (which, btw, can't even happen with DM), well, thats why they call it a black swan.  You can't foresee it so theres no sense in thinking about the event.

[DSTAVERT]

I realize you can't. The only possible thing is to under provision and let DM increase as necessary.  If you under provision everything to take advantage of DM you can in effect over commit. What solutions are there for that condition.

This assumes you don't pay any attention to your environment.

Let me clarify. We over provision to a level that prevents constant out of memory situations.