MongoDB may cause excessive disk space usage when Zlib compression is enabled.
Disk space could be consumed rapidly causing out of space errors. Upgrading to a version that contains the fix will not reclaim the excess disk space; for that, a re-write of the collection data with a version containing the fix is needed (e.g.: initial sync).
There is currently no workaround for this issue.
MongoDB production releases 3.6.0 through 3.6.8 as well as 4.0.0 and 4.0.1 are affected by this issue.
This issue is fixed in MongoDB version 3.6.9 and 4.0.2
Please consider upgrading to 3.6.9 or 4.0.2 if this issue impacts you.