docs(maintenance): Remove S3 and MMR reference

* Also subsectioned btrfs stuff for database

docs/maintenance.mdx

@@ -48,7 +48,11 @@ troubleshooting](./troubleshooting.mdx#rocksdb--database-issues).
 ### Compression
 
 Some RocksDB settings can be adjusted such as the compression method chosen. See
-the RocksDB section in the [example config](./reference/config.mdx).
+the RocksDB section in the [example config](./reference/config.mdx), and the
+[database compression section](./guides/performance.mdx#tuning-database-compression)
+in the perf-tuning documentation for more.
+
+#### Caveats for btrfs users
 
 btrfs users have reported that database compression does not need to be disabled
 on Continuwuity as the filesystem already does not attempt to compress. This can be
@@ -58,10 +62,12 @@ to ensure no additional filesystem compression takes place as this can render
 unbuffered Direct IO inoperable, significantly slowing down read and write
 performance. See [the Btrfs docs](https://btrfs.readthedocs.io/en/latest/Compression.html#compatibility).
 
-> Compression is done using the COW mechanism so it’s incompatible with
-> nodatacow. Direct IO read works on compressed files but will fall back to
-> buffered writes and leads to no compression even if force compression is set.
-> Currently nodatasum and compression don’t work together.
+:::important
+Compression is done using the COW mechanism so it’s incompatible with
+`nodatacow`. Direct IO read works on compressed files but will fall back to
+buffered writes and leads to no compression even if force compression is set.
+Currently `nodatasum` and compression don’t work together.
+:::
 
 ### Files in database
 
@@ -134,15 +140,9 @@ the file created time (`btime`) or file modified time (`mtime`)
 See the [`!admin media` commands](./reference/admin/media.md) for further information.
 All media in Continuwuity is stored at `$DATABASE_DIR/media`.
 
-If you are finding yourself needing extensive granular control over media, we
-recommend looking into [Matrix Media
-Repo](https://github.com/t2bot/matrix-media-repo). Continuwuity intends to
-implement various utilities for media, but MMR is dedicated to extensive media
-management.
-
-Built-in S3 support is also planned, but for now using a "S3 filesystem" on
-`media/` works. Continuwuity also sends a `Cache-Control` header of 1 year and
-immutable for all media requests (download and thumbnail) to reduce unnecessary
-media requests, bandwidth, and load.
+While Continuwuity does not implement built-in S3 support, using an "S3 filesystem
+on the `media/` path will works. Continuwuity also sends a `Cache-Control` header
+of 1 year and immutable for all media requests (download and thumbnail)
+to reduce unnecessary bandwidth and load.
 
 [rocksdb-compaction]: https://github.com/facebook/rocksdb/wiki/Compaction