diff --git a/files/prometheus/prometheus.service b/files/prometheus/prometheus.service
index 6007b73..512d9c9 100644
--- a/files/prometheus/prometheus.service
+++ b/files/prometheus/prometheus.service
@@ -15,7 +15,7 @@ ExecStart=/usr/sbin/prometheus \
     --web.config.file=/etc/prometheus/web-config.yaml \
     --storage.tsdb.path /prometheus-data/ \
     --storage.tsdb.retention.time 70d \
-    --storage.tsdb.retention.size 15GB \
+    --storage.tsdb.retention.size 12GB \
     --storage.tsdb.max-block-duration=2h \
     --storage.tsdb.min-block-duration=2h \
     --web.enable-remote-write-receiver \