diff --git a/howto/ganeti.md b/howto/ganeti.md
index 1a34e9e44102fa451d57135902a7a325f4afa385..b4ba716eb3a016a0ed8944ed7cb6832911479f14 100644
--- a/howto/ganeti.md
+++ b/howto/ganeti.md
@@ -461,6 +461,24 @@ on teh `vg_ganeti_hdd` volume group, which is "slow" rotating disks:
     gnt-instance modify --disk add:size=100g,vg=vg_ganeti_hdd test1.torproject.org
     gnt-instance reboot test1.torproject.org
 
+### Changing disk type
+
+If you have, say, a test instance that was created with a `plain` disk
+template but we actually want it in production, with a `drbd` disk
+template. Switching to `drbd` is easy:
+
+    gnt-instance shutdown test-01
+    gnt-instance modify -t drbd test-01
+    gnt-instance start test-01
+
+The second command will use the allocator to find a secondary node. If
+that fails, you can assign a node manually with `-n`.
+
+You can also switch back to `plain`, although you should generally
+never do that.
+
+See also the [upstream procedure](https://docs.ganeti.org/docs/ganeti/3.0/html/admin.html#conversion-of-an-instance-s-disk-type) and [design document](https://docs.ganeti.org/docs/ganeti/3.0/html/design-disk-conversion.html).
+
 ### Adding a network interface on the rfc1918 vlan
 
 We have a vlan that some VMs that do not have public addresses sit on.