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MCSDIF.vhdx growing to a large size

Anthony Yates1709157372



Citrix Virtual Apps 7 1912 LTSR CU1

Windows Server 2012 R2


We've recently moved our users over to a new Citrix build that contained many updates/changes to the previous build, such as replacing Office 2007 with Office 2016, usual updates we routinely apply like Windows Updates, AV updates, Chrome, applications etc. These we done over a number of image updates and we had a number of users trialling the new build before we moved everyone across. However it wasn't until we started getting 30+ users per session host that we noticed the MCSDIF.vhdx growing to a very large size and if we do not reboot the server after about 3 days usage it will fill the disk.


Now our C: drive is about 80GB (30.5GB Used) and I've only allocated about 40GB to the MCS difference disk, and I know I could increase this to avoid the issue or increase RAM cache etc. But I would like to understand how or why we are getting such are large increase in differences as we never had this issue in our old build. And I'm concerned that if its needing to use MCSDIF so much that it will impact performance.


Is there any way to identify what is generating so many changes to the disk that was causing MCSDIF to grow so large.

I've used performance monitor for clues and I can see high page file activity around the same time mcsdif is increasing in size but page file is on D: drive not C: drive and there is plenty of spare memory available.




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On 2/5/2021 at 8:54 PM, Patrick Matula said:

Hi Anthony, 


I wrote an article for PVS. 

PVS target device - full cache


I don't know much about MCS, but I could imagine that you can do the same procedure to solve the issue. 

I would appreciate it if you tell me if my article helped or not :-)


Thanks for that. That is useful, just the mention of Outlook cache made we wonder if it was that, but it doesn't appear to be ost files.

However, I will try your procedure to see if it can identify the cause. If I get time later today I will try it today, I'll let you know how it goes.


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