[pbs-devel] [PATCH proxmox-backup] docs: add note on supported filesystems

[Stoiko Ivanov <s.ivanov@proxmox.com>]

certain filesystems cannot be used as chunkstores, because they don't
support 2^16 subdirectories (e.g. ext4 with certain features disabled
or ext3 - see ext4(5))

reported via our community forum:
https://forum.proxmox.com/threads/emlink-too-many-links.73108/

Signed-off-by: Stoiko Ivanov <s.ivanov@proxmox.com>
---
 docs/administration-guide.rst | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/docs/administration-guide.rst b/docs/administration-guide.rst
index 1f329f80..e48f115a 100644
--- a/docs/administration-guide.rst
+++ b/docs/administration-guide.rst
@@ -139,6 +139,12 @@ or ``zfs``) to store the backup data.
 Datastores are identified by a simple *ID*. You can configure it
 when setting up the backup server.
 
+.. note:: The `File Layout`_ requires the file system to support more than
+   65537 subdirectories per directory. This excludes certain filesystems and
+   filesystem configuration from being supported as datastore. For example
+   ``ext4`` without the ``dir_nlink`` feature (which is enabled by default)
+   and ``ext3``.
+
 
 
 Datastore Configuration
-- 
2.20.1