updating etcd manual defragmentation docs

Author: lahinson

modules/etcd-defrag.adoc

@@ -51,11 +51,16 @@ failed defrag on member: __<member_name>__, memberID: __<member_id>__: __<error_
 [id="manual-defrag-etcd-data_{context}"]
 == Manual defragmentation
 
-You can monitor the `etcd_db_total_size_in_bytes` metric to determine whether manual defragmentation is necessary.
+//You can monitor the `etcd_db_total_size_in_bytes` metric to determine whether manual defragmentation is necessary.
+
+A Prometheus alert indicates when you need to use manual defragmentation. The alert is displayed in two cases:
+
+   * When etcd uses more than 50% of its available space for more than 10 minutes
+   * When etcd is actively using less than 50% of its total database size for more than 10 minutes
 
 [WARNING]
 ====
-Defragmenting etcd is a blocking action. The etcd member will not response until defragmentation is complete. For this reason, wait at least one minute between defragmentation actions on each of the pods to allow the cluster to recover.
+Defragmenting etcd is a blocking action. The etcd member will not respond until defragmentation is complete. For this reason, wait at least one minute between defragmentation actions on each of the pods to allow the cluster to recover.
 ====
 
 Follow this procedure to defragment etcd data on each etcd member.
@@ -182,3 +187,7 @@ memberID:12345678912345678912 alarm:NOSPACE
 ----
 sh-4.4# etcdctl alarm disarm
 ----
+
+.Next steps
+
+After defragmentation, if etcd still uses more than 50% of its available space, consider increasing the disk quota for etcd.