There are few queries here,
1> Are you dealing with Linear array or Virtual Array?
2> 100% full you mean by space or by CPU utilization or something else ?
If your question related to 20% space left at the WIndows Host for the Volume presented from MSA then from array perspective if this is linear array which means space alreay fully allocated so doesn't matter from array. So only we can consider Windows filesystem level impact. For any windows system and any drive if space is less free that means system need to find free space to write new IOs which may take time and that's why it may hit performance.
If your question related to Virtual Array then also 20% space left will be subjective to how much space got allocated out of the thin provisioned size from array for that thin volume. This time also Windows file system level impact may be same but from array perspective less space got allocated so block level some relief.
Hope this helps!
Regards
Subhajit
I am an HPE employee
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