diff --git a/group_vars/metricspi/alerts.yml b/group_vars/metricspi/alerts.yml
index fdac376..9e57768 100644
--- a/group_vars/metricspi/alerts.yml
+++ b/group_vars/metricspi/alerts.yml
@@ -85,6 +85,17 @@ vmalert_rules:
           something happens to the active disk, such as hardware failure, power
           surge, fire, or accidental `rm -rf`, the offline disk is only out of
           date by a few weeks.
+    - alert: disk needs archived
+      expr:
+        collectd_md_md_disks{instance="burp1.pyrocufflink.blue", type="missing"} < 1
+      annotations:
+        summary: One of the disks in the BURP array should be archived
+        description: >-
+          The disks in the BURP RAID-1 (mirror) array should be swapped
+          periodically.  One disk should be online and mounted while the other
+          is stored in the fireproof safe.  All of the disks are currently
+          online; one needs to be disconnected and moved to the safe as soon as
+          possible.
 
   - name: certificates
     rules: