Skype for Business Inplace Upgrade – Undocumented Disk Space Requirements

It’s fairly well blogged and documented that you’ll need ‘a disk’ with ‘at least 32 Gb free’ to be able to perform the Skype for Business in-place upgrade.

The pre-requisite checker even tells you…

Before this server can be upgraded, the following must be resolved:
Unable to find suitable drives for Inplace Upgrade. Upgrade requires an uncompressed local disk with at least 32 GB of available free space, formatted in NTFS.

But, I recently encountered an environment where the Wizard passed this pre-requisite check with flying colours, the server indeed had a disk with at least 32GB free space, and yet failed on the last but one step of the installation wizard.

The step “Installing roles…” produced this old chestnut (Christmas reference)…

Install-CsDatabase was unable to find suitable drives for storing the database files. This is often due to insufficient disk space; typically you should have at least 32 GB of free space before attempting to create databases. However, there are other possible reasons why this command could have failed. For more information, see

Yet, this server did… It had over 74Gb free space on D: – which last time I checked, is both ‘a disk’ and has ‘at least 32Gb free’.

The link just goes straight to the Install-CsDatabase cmdlet on TechNet, no futher information about this issue. No mention of what the ‘other possible reasons’ could be.

Also to put it in perspective, this was the 17th Front End Server upgraded as part of this project, in the 3rd pool to be upgraded, and yet the 1st to show this error.

All previous servers had roughly 8-14GB free space on C:, and each well over 32GB on a D: drive. and never showed a disk space warning.

There was no obvious difference why this server couldn’t find a ‘suitable disk’.

Troubleshooting steps confirmed…

  • SQL Services were running, and SQL Instance was operational.
  • SQL default path for Data and Logs was both on D:
  • All Databases attached to the SQL Server Instance were also located on D: (both data, and logs).
  • Drive was not ‘compressed’.
  • PowerShell cmdlet run manually (outside of the Wizard) displayed the same error.
  • Servers rebooted, disk space checked again.

The Issue and Fix

After period of head scratching, we had confirmation back from Microsoft that this scenario has been encountered before with other customers…

Apparently, if at any point in time, the CSDATA directory had been located on C:, the disk space check *may* incorrectly include it in it’s logic, regardless of the location of the databases currently. And requires at least 16GB free space where the databases USED TO BE LOCATED!?

Luckily it was possible to scrounge a few extra gigabytes to push the free space on C: up over 16GB, and the installation continued along peacefully from that point.

Needless to say if you were anywhere near at the time, you would have heard desperate and tired screams of “BUT IT DOES HAVE ENOUGH FREE SPACE!!!” for miles around.

Thanks Microsoft, would it have pushed the product over budget, or delayed release beyond launch day to simply include the drive letter in the error message?

Thanks for reading

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About Graham Cropley

Working as a Senior Consultant for Skype for Business, Exchange, and Office 365.


  1. Dont sorry Graham, MSFT usually fixed such defects only in the Next major release. And they think we should be thankful about this…

  2. Thanks for this post Graham! I had the exact same issue, except I took the path of deleting temp directories, uninstalling things we didn’t need, expanding disk and rebooting 5-10 times! Your way is much easier and saves so much more time! d;-)

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