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Windows 10 pooled VDI memory and CPU sizing query


John Morrissey

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Hi all,

In the midst of looking to purchase kit for a 1500 user windows 10 VDI environment. At present users are running in a hosted shared environment(2008 r2 published desktops) and as the hardware they are running is out of maintenance soon need to buy new kit.

From a sizing perspective have been pondering how much memory / VCPU we'll need. Want to err on the side of caution and go with the "heavy" recommendation of 

8gb RAM 2vCPU.

Going 1:1 and doing the sums on that figure indicates I would need 12TB of RAM and 3000vCPU ports which seems pretty astronomical - my query is have other folks got experience

in sizing for this?

The workload would be pretty standard office 2016 / skype (at present but will be replaced with teams later this year). Would of course look to optimize the image (no appx,cortana,defender,search etc)

 

Any thoughts regards memory/vCPU sizing really appreciated ! (for storage looking into that separately) - just looking at a 1:1 sizing perspective the specs look huge so any real world experience here would be great

 

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Hi,

 

I wouldn't do 1:1 for the CPUs, it's not needed for that type of user. Even if you give the desktops 2 vCPUs, pessimistically, they'll probably never use more than 1 GHz most of the time, so depending on the clock-speed of the CPU's you choose, you divide the clock speed by 1, then multiply by the amount of physical cores. Don't count the hyper-threads, they only add about a 20% performance increase, and are best used as a buffer for spikes.

So an example: let's say you go with 2x 24-core Intel Scalable Gold 6252, at 2.1 GHz, that would mean you could get 96 users on that system.

For that amount of users, I would look into AMD EPYC 7002 though, more cores, higher clock speed and cheaper than Intel Scalable.

 

For the memory, 8 GB also seems a bit much for that type of user, especially if you would be looking to optimise the image. 6 GB would be more than enough, even 4 GB would probably be doable.
That said, memory is not going to be your limiting factor in your systems anyway, it will be CPU.

 

Hope that helps,

 

Koenraad

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We have done the same sizing activity recently for the move from XenApp shared server desktops to Win10 VDI. In regards to spec'ing the actual VDI desktops themselves, nobody here will be able to tell you what you are going to need accurately as only you know how your business and your users actually work day to day.  There is no point in over spec'ing them too much as you will waste money/density on the host but if you see users chomping through 8gb of Ram more than not it maybe needed. 

 

What HyperVisor would you be running these from out of curiosity? would you be needing any fail over requirements for the business? room for user growth without buying in new kit each time?

 

In regards to how many VDIs you can run on one host server, we found this article interesting- https://www.citrix.com/blogs/2017/03/20/citrix-scalability-the-rule-of-5-and-10/ a little old now but still relevant. We got together 6 or so different server specs and then did the sizing calculations for CPU & memory on each showing basically the more you pay for hardware the better the VDI density. 

 

The issue with sizing activities is you can go too granular really easily trying to account for every singe thing and it will drive you insane. Its good to get strong base set of numbers but you will never fully know how its panning out until you start moving users onto the new VDI platform and monitoring closely.  

 

We here are looking into the AMD stuff and Dell are sending us a test server soon so we can do some bench marking against the current Intel kit. Depending on your project budget Dell even offer a tiny 1u rack server with x2 AMD CPUs (2.3GHz clock) and 128 physical cores total! stick 1tb of ram in there and you have some great density. 

 

 

 

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