Manual:$wgCompressRevisions/de

Details
Falls diese Option aktiviert ist, werden alle zukünftigen Seitenversionen beim Speichern komprimiert, aber nur, falls zlib in PHP vorhanden und aktiviert ist.

We can also compress text in the old revisions; for this, use the script located in directory /maintenance/storage. Any compressed revisions will be decompressed on load regardless of this setting but will not be readable at all if zlib support is not available.

Note
Once you enable, the compressed texts will no longer be searchable/replaceable via SQL scripts. This means any extension require SQL search/replace will not able to work. If you want these extension work, try to run periodically instead of enable.