Comments on: Hyper-V [Not Exactly] Dynamic Memory

By: VMware vSphere offers the most comprehensive memory management and configuration capabilities | VCritical

Fri, 17 Jun 2011 00:04:43 +0000

[...] piece pits VMware vSphere memory management technologies against the new Microsoft Hyper-V Dynamic Memory. While certainly an interesting topic, I was disappointed by some of the inaccurate statements [...]

By: Fernando

Fernando — Sat, 25 Dec 2010 03:03:43 +0000

Sorry, I was not clear on my reply .. I acknowledge the info you gave about standard version, I was just adding more info here, sorry.

By: Stu Fox

Stu Fox — Sat, 25 Dec 2010 02:35:42 +0000

Also looks like you didn’t actually read my reply – hot add does not use the hot add framework that was traditionally used for adding memory to physical systems (so the Standard/Enterprise distinction doesn’t matter). Again, rather than me tell you it’s different, if you really want to know, go watch one of those TechEd recordings. I know this is a VMware site and you’re not inclined to do so, but until you do you’re coming from an uninformed position.

Cheers & Merry Christmas

Stu

By: Fernando

Fernando — Fri, 24 Dec 2010 19:33:07 +0000

Thanks Eric,

Enterprise version cost 4 times more than standard, and historically does not have all features (such as hot add). That’s why many organizations use standard version for almost everything, leaving Ent for clusters, etc etc
But looks like MS fixed it.

By: Fernando

Fernando — Fri, 24 Dec 2010 19:31:44 +0000

No matter the terminology mess MS is doing with this, DM is copy of VMware proven ballooning technique, plus this hot add stuff.
In the end, the objective is to accommodate more VMs in the host, which is called, guess what … overcommit !

Funny to see you guys implementing something you criticize for so long, with some terminology changed to not look the same.
It reminds me the “Who needs VMotion ??” message from MS some time ago.

By: Eric Gray

Eric Gray — Thu, 23 Dec 2010 23:46:00 +0000

Let’s forgive Fernando for not being up to date with the latest breaking news — when Dynamic Memory was first announced, Enterprise or Datacenter were required. It turned out that some customers had standardized on Standard, no pun intended, and a hotfix was planned to accommodate that scenario.

By: Phil

Phil — Wed, 22 Dec 2010 15:25:18 +0000

Fernando, rather than just making a bunch of (incorrect) assumptions, would it not be better to find out the facts first?

As for the actual blog posting, well its no more than the usual VMWare FUD is it really. “Dynamic Memory is clearly a non-starter for things like Oracle databases and Java applications that are tuned for specific resources” – Because you always install an enterprise database and throw it straight out into production with no further config changes don’t you?

By: Stu Fox

Stu Fox — Wed, 22 Dec 2010 01:32:18 +0000

Fernando, rather than me telling you that “it isn’t like it is in the VMware world” repeatedly, if you want to know how this really works you should have a look at one of Ben Armstrongs sessions from TechEd, available online at http://www.msteched.com. He covers the nuts and bolts of how it works.

To your point about hot add support, it doesn’t use the Windows hot add framework to add memory which means that support for Windows 2003 is there (it’s available right now in the RC release of SP1).

I probably should have put my disclaimer: I work for Microsoft.

By: Fernando

Fernando — Tue, 21 Dec 2010 23:51:57 +0000

I think that it is at least strange to have VMs with huge memory sizes, and the ballon inflated all times. I bet some applications would have trouble with that , and they were never designed with this in mind.
Even windows auto tune some parameters based on the total memory. If you add memory all time, you are playing a trick to the OS and applications.

Many applications will not be able to take advantage of this additional memory immediately.

Windows server 2003 standard does not support hot add (from my knowledge), so, I don’t think 80% of the OSes is a correct number (depend on how updated the customer is with latest MS OSes).

By: Stu Fox

Stu Fox — Tue, 21 Dec 2010 20:28:18 +0000

Fernando that would be of course if you viewed DM through a VMware lens. The ballooning driver removes the memory from the VM as it needs to, making it available for the host to allocate to another VM. The VM will not be oversized, it will be using as much memory as it needs. Should it require the memory again, DM will ensure that it has it. The balloon being inflated actually doesn’t matter. I’m not sure how this works on VSphere, but it sounds like it’s slightly different.
Configuring a min/max isn’t really that much of an issue – you already set a maximum anyway, this just adds a startup figure, you can script it if you want. Peak usage on the VM triggering a hot add is exactly what dynamic memory is for, it’s not actually a drawback. Sure, it only works on OSes that support hot add on Hyper-V, but that just happens to be 80% of the target market anyway (Win2k3 and above).