Storage Spaces Direct - S2D - Rebuild Size after Maintenance on a Node

[petben]

Hello, we have a Storage Spaces Direct 2 node test cluster. We are finding that if we put one node into maintenance mode (drain the VM's to apply Windows updates or similar) the size of the rebuild data is HUGE after just a few minutes. We have 4TB in total of test VM's on the cluster and after 20 mins of running on a single node and not really doing much to the VM's S2D reports ~1TB of changes to be written back, we can literally refresh the PowerShell command and watch it jump up in size in multiple GB's. Has anyone else found this, there doesn't seem to be any settings for write back block size or any other settings.

 

 

Thanks for any info