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VMware Thin vs Thick Eager on a 7200

JCutter
Occasional Visitor

VMware Thin vs Thick Eager on a 7200

Hello everyone, I've done some looking but couldn't find an exact response to this so I figured I would ask here. 

 

I have an ESXI 5.5 environement and we bought a 7200 and we are going to use all Thin Virtual Volumes.

 

The problem I'm having is determining whether we do Thin or Thick Eager for the VM's themselves. I looked in the HP 3PAR StoreServ Storage and VMware vSphere best practices guide and they say specifically that Thick Eager Zero is the way to go and that "administrators should realize that there are no additional storage savings realized by using VMware Thin Provisioning on top of TPVVs" 

 

That problem with that is... there is a savings from what I'm seeing unless I am seeing this wrong. 

Lets say for example I have a Virtual Volume that is 100GB big. I put a thin VM on there that is 80GB big but only 20GB is used. The Storage and VMWare both see it as having 80GB free now. That all makes perfect sense.  The problem I have is by going with the best practices guide and turning that VM into a thick Eager. After switching it to thick Eager the ESXI sees a datastore that only has 20GB free but the 7200 sees it as using only 20GB still. I am actually losing space on the disk storage because I have to keep throwing more space at it even though the 7200 isnt really using all the space. 

What is the common way to go about this? What are others doing? Am I missing something?

Any help would be greatly appreciated.

 

Thanks!
Joe

2 REPLIES
JCutter
Occasional Visitor

Re: VMware Thin vs Thick Eager on a 7200

Anyone have any idea on this one? I dont know if this is supposed to work this way or not. I would think it wouldnt. I would think if HP is saying go Thick Eager VMware should be seeing the space free that the 3Par is.

 

Any help would be appreciated.

 

Thanks!

Sheldon Smith
Honored Contributor

Re: VMware Thin vs Thick Eager on a 7200

You're not losing any space. The question is where do you want to manage the space? You're looking at the problem from the wrong direction.

 

Let's say you have a VM that's 80GB, with only 20GB in use. You create a virtual volume that is 80GB, make the datastore and move the VM as thick eager to it. The 80GB datastore is now full; it has an 80GB VM on it. But the 7000 only needed to allocate 20GB of physical storage to it.
You have another VM that's 500GB, but only 70GB in use. Again, you create a 500GB virtual volume / datastore, and move the thick eager VM to that. As far as vCenter is concerned, you have almost 600GB of VMs running. So? They only needed 90GB of storage.


Thin Provisioning works on the basis of you having a bunch of VMs wanting storage, but none of them are really using what they requested. Not only are you not losing space on the disk storage, you are saving it because what has been requested may not be used for another year or more. Until then, the physical storage can be used elsewhere.
Eventually, you will need to add physical storage, since the current physical storage will be consumed with real allocations. But the total provisioned to vCenter can be significantly greater than the physical storage you have to buy NOW.


Note: While I work for Hewlett Packard Enterprise, all of my comments (whether noted or not), are my own and are not any official representation of the company.
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