Add notes about increasing disk size

docs/disk-increase.md

@@ -0,0 +1,17 @@
+Below are some notes on how to resize the disks when a new drive is added to
+our dedicated hosts:
+
+```
+fdisk /dev/nvme3n1
+# create gpt partition table and new RAID 5 (label 42) partition using the CLI 
+mdadm --manage /dev/md3 --add /dev/nvme3n1p1
+cat /proc/mdstat
+# Take note of the volume count (4) and validate that nvme3n1p1 is marked as spare ("S")
+mdadm --grow --raid-devices=4 /dev/md3
+```
+
+```
+# resize2fs /dev/md3
+# df -h | grep md3
+/dev/md3        2.6T  1.2T  1.3T  48% /
+```