diff --git a/2025/xg-infra-upgrade-2025.md b/2025/xg-infra-upgrade-2025.md
index 6b5f79c..ce50f1b 100644
--- a/2025/xg-infra-upgrade-2025.md
+++ b/2025/xg-infra-upgrade-2025.md
@@ -102,3 +102,7 @@ data/test-dataset/dataset-1   128M   410G   128M  /data/test-dataset/dataset-1
 * [[freebsd-jail-vanilla]]
 * [[So you wanna do FreeBSD 14.1 and native Home Assistant?]]
 * [[computers-and-machines]]
+
+# External docs
+
+* https://klarasystems.com/articles/openzfs-understanding-zfs-vdev-types/