doc: describe how to enlarge btrfs volumes

This might be handy;  while on it, I'm removing the part that relates to
resizing backend volume (we now have RAID10 volume, and a separate doc).

doc/enlarge_volumes.rst

@@ -0,0 +1,45 @@
+.. _enlarge_volumes:
+
+How to enlarge disk partitions
+==============================
+
+This document describes how to enlarge Fedora Copr infrastructure volumes hosted
+in AWS.
+
+
+How to enlarge btrfs non-data partitions
+----------------------------------------
+
+At some point, Fedora Cloud images moved to btrfs and we inherited those.  From
+time to time we need to enlarge `/` partition, or alike.  We don't do
+"snapshots" in this part becase we don't treat the critical (data) volumes.
+
+1. `Login to AWS`_, find the volume in question, and enlarge accordingly
+2. SSH to the corresponding machine, and run something like::
+
+    [root@copr-fe copr-frontend][PROD]# growpart /dev/nvme0n1 5
+    CHANGED: partition=5 start=2265088 old: size=102592479 end=104857567 new: size=144535519 end=146800607
+
+    [root@copr-fe copr-frontend][PROD]# btrfs filesystem resize max /
+    Resize device id 1 (/dev/nvme0n1p5) from 48.92GiB to max
+
+
+How to enlarge other partititions
+---------------------------------
+
+1. `Login to AWS`_, find the volume in question
+2. In case something goes wrong, you may create a snapshot with the same tags
+   the volume already has (see instructions in AWS Tips-and-Tricks).  Name it so
+   that the snapshot can then be distinguished from the others, because after
+   enlarging the disk it will be deleted. Note that creating the snapshot can
+   take quite some time.
+3. Enlarge the volume accordingly (may take hours, if we speak about TBs)
+4. SSH to the VM, and run something like::
+
+    $ nvme reset /dev/nvme1  # NOTE! we don't have to do this anymore, check lsblk
+    $ growpart /dev/nvme1n1 1
+    $ resize2fs /dev/nvme1n1p1
+
+5. Delete the snapshot from step 2, if any.
+
+.. _`Login to AWS`: https://id.fedoraproject.org/saml2/SSO/Redirect?SPIdentifier=urn:amazon:webservices&RelayState=https://console.aws.amazon.com

doc/maintenance_documentation.rst

@@ -20,7 +20,7 @@ This section contains information about maintenance topics. You may also be inte
    :maxdepth: 1
 
    aws_tips_and_tricks
-   enlarge_disk_copr_be
+   enlarge_volumes
    raid_on_backend
    backup_recovery