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Kevin Remde is an IT Pro Evangelist, which is a fancy title that just means "a guy who geeks-out about information technology and how software can improve business and home life; and isn't afraid to tell people about it in whatever way he can". When he's not learning about or blogging about new technologies, Kevin enjoys digital photography and videography, and sings in a band. (Q: Midlife crisis? A: More cowbell!) He continues to challenge his TechNet Event audiences throughout the central region of the country to sing Karaoke with him. Kevin is a DZone MVB and is not an employee of DZone and has posted 24 posts at DZone. You can read more from them at their website. View Full User Profile

Dynamic Memory – Not Your Father’s Memory Overcommit: Part 3

03.08.2013
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Part 3 of our “20+ Days of Server Virtualization” series is about Dynamic Memory in Hyper-V.  As the title suggests, this is not your Father’s Memory Overcommit.

“Memory Overcommit?  Isn’t that a VMware capability?”

In the context of virtualization, yes.  (It may be something addressed in the field of Neuroscience, but I’m no rocket scientist…)

Before we talk about it, let’s take a look at the word “Overcommit” (from The Free Dictionary):

O·ver·com·mit (vr-k-mtv. o·ver·com·mit·tedo·ver·com·mit·tingo·ver·com·mits v.tr.

  1. To bind or obligate (oneself, for example) beyond the capacity for realization.
  2. To allocate or apportion (money, goods, or resources) in amounts incapable of replacement.

v.intr.

  1. To be or become overcommitted.

That phrase “beyond the capacity for realization” is important.  To overcommit memory means to obligate more memory be used than the capacity we actually physically have. 

“Is that a good thing?”

It can be, if, in the case of the consolidation ratios of virtual machines on a physical host, it’s more important for you to pack more onto a box than it is to get decent performance out of those virtual machines.

“Dynamic Memory” is Microsoft’s solution (in Hyper-V) to do something similar.  But in this case, Microsoft does not overcommit.  By contrast, it allocates memory to or from VMs sharing a virtualization host based on the memory demand of the VMs. 

Today in Part 3, my friend Dan Stolts expands on this definition and these technologies for us.

READ HIS EXCELLENT ARTICLE HERE

Published at DZone with permission of Kevin Remde, author and DZone MVB. (source)

(Note: Opinions expressed in this article and its replies are the opinions of their respective authors and not those of DZone, Inc.)