Improve mergerfs intro in docs (#1563)

mkdocs/docs/index.md

@@ -1,14 +1,41 @@
 # mergerfs - a featureful union filesystem
 
-**mergerfs** is a
-[FUSE](https://en.wikipedia.org/wiki/Filesystem_in_Userspace) based
-[union filesystem](https://en.wikipedia.org/wiki/Union_mount) geared
-towards simplifying storage and management of files across numerous
-commodity storage devices. It is similar to [**mhddfs**, **unionfs**,
-**aufs**, **DrivePool**, etc.](project_comparisons.md) Allowing for
-the aggregation of storage without the more rigid requirements and
-failure conditions of [RAID and other
-technologies](project_comparisons.md).
+**mergerfs** is a [union
+filesystem](https://en.wikipedia.org/wiki/Union_mount) that makes
+multiple storage devices or filesystems appear as a single unified
+directory. Built on [FUSE (Filesystem in
+Userspace)](https://en.wikipedia.org/wiki/Filesystem_in_Userspace), it
+is designed to simplify how you manage files across several
+independent filesystems without the complexity, fragility, or cost of
+RAID or similar storage aggregation technologies.
+
+Think of mergerfs as a smart pooling layer: you can combine any number
+of [existing
+filesystems](faq/usage_and_functionality.md#can-mergerfs-be-used-with-filesystems-which-already-have-data)
+— whether they are on hard drives, SSDs, network shares, or other
+mounted storage — into what looks like one large filesystem, while
+still maintaining direct access to each individual filesystem. Unlike
+RAID, there's no rebuild process if a device fails. You only lose the
+files that were on that specific filesystem. You can also add or
+remove filesystems at any time without restructuring your entire pool.
+
+mergerfs excels at cost-effective storage expansion, making it ideal
+for media libraries, backups, archival data, and other write-sometimes,
+read-often workloads where you need lots of space but don't want
+the overhead of traditional storage technologies.
+
+**Key advantages:**
+
+* Mix and match filesystems of any size, type, or underlying device
+* No parity calculations or rebuild times
+* Add or remove filesystems on the fly
+* Direct access to files on individual filesystems when needed
+* Flexible policies for controlling where new files are created
+
+For users seeking alternatives to mhddfs, unionfs, aufs, or DrivePool,
+mergerfs offers a mature, actively maintained solution with extensive
+configuration options and documentation. See the [project comparisons
+for more comparisons.](project_comparisons.md)
 
 
 ## Features
@@ -19,7 +46,7 @@ technologies](project_comparisons.md).
 * Ability to add or remove filesystems/paths without impacting the
   rest of the data
 * Unaffected by individual filesystem failure
-* Configurable file selection and creation placement
+* Configurable file creation placement
 * File IO [passthrough](config/passthrough.md) for near native IO
   performance (where supported)
 * Works with filesystems of any size
@@ -28,7 +55,7 @@ technologies](project_comparisons.md).
 * Ignore read-only filesystems when creating files
 * [Hard links](faq/technical_behavior_and_limitations.md#do-hard-links-work)
 * Hard link [copy-on-write / CoW](config/link-cow.md)
-* [Runtime configurable](runtime_interface.md)
+* [Runtime configurability](runtime_interface.md)
 * Support for extended attributes (xattrs)
 * Support for file attributes (chattr)
 * Support for POSIX ACLs
@@ -36,12 +63,14 @@ technologies](project_comparisons.md).
 
 ## Non-features
 
-* Read/write overlay on top of read-only filesystem like OverlayFS
-* File whiteout
 * RAID like redundancy (see [SnapRAID](https://www.snapraid.it) and
   [NonRAID](https://github.com/qvr/nonraid))
-* Redundancy
+* LVM/RAID style block device aggregation
+* Data integrity checks, snapshots, file versioning
+* Read/write overlays on top of read-only filesystems (like OverlayFS)
+* File whiteout
 * Splitting of files across branches
+* Active rebalancing of content
 
 
 ## How it works
@@ -62,7 +91,7 @@ For functions which change attributes or remove the file the behavior
 may be applied to all instances found.
 
 The way in which mergerfs behaves is controlled by the
-[config/options/settings](config/options.md). More specifically by
+[config / options / settings](config/options.md). More specifically by
 [policies](config/functions_categories_policies.md).
 
 
@@ -90,7 +119,6 @@ A         +      B        =       C
 +-- file7        +-- file7        +-- file7
 ```
 
-
 ## Getting Started
 
 Head to the [quick start guide](quickstart.md).
@@ -107,3 +135,6 @@ Head to the [quick start guide](quickstart.md).
   like something is not explained sufficiently or missing please [ask
   in one of the supported forums](support.md#contact-issue-submission)
   and the docs will be updated.
+* The search feature of MkDocs is not great. Searching for "literal
+  strings" will generally not work. Alernative solutions are being
+  investigated.