add information about ingester storage volumes to scaling guide

content/influxdb/clustered/admin/scale-cluster.md

@@ -276,6 +276,44 @@ The Ingester can be scaled both [vertically](#vertical-scaling) and
 Vertical scaling increases write throughput and is typically the most effective
 scaling strategy for the Ingester.
 
+#### Ingester storage volume
+
+Ingesters use an attached storage volume to store the
+[Write-Ahead Log (WAL)](/influxdb/clustered/reference/glossary/#wal-write-ahead-log).
+With more storage available, Ingesters can keep bigger WAL buffers, which
+improves query performance and reduces pressure on the Compactor.
+Storage speed also helps with query performance.
+
+Configure the storage volume attached to Ingester pods in the
+`spec.package.spec.ingesterStorage` property of your `AppInstance` resource. 
+
+{{< expand-wrapper >}}
+{{% expand "View example Ingester storage configuration" %}}
+
+{{% code-placeholders "STORAGE_(CLASS|SIZE)" %}}
+
+```yml
+apiVersion: kubecfg.dev/v1alpha1
+kind: AppInstance
+# ...
+spec:
+  package:
+    spec:
+      # ...
+      ingesterStorage:
+        # (Optional) Set the storage class. This will differ based on the K8s
+        #environment and desired storage characteristics.
+        # If not set, the default storage class is used.
+        storageClassName: STORAGE_CLASS
+        # Set the storage size (minimum 2Gi recommended)
+        storage: STORAGE_SIZE
+```
+
+{{% /code-placeholders %}}
+
+{{% /expand %}}
+{{< /expand-wrapper >}}
+
 ### Querier
 
 The Querier can be scaled both [vertically](#vertical-scaling) and

content/influxdb/clustered/reference/glossary.md

@@ -1131,15 +1131,17 @@ A statement that sets or updates the value stored in a variable.
 
 ## W
 
-### WAL (Write Ahead Log) - enterprise
+### WAL (Write-Ahead Log)
 
 The temporary cache for recently written points.
 To reduce the frequency that permanent storage files are accessed, InfluxDB
 caches new points in the WAL until their total size or age triggers a flush to
-more permanent storage. This allows for efficient batching of the writes into the TSM.
+more permanent storage. This allows for efficient batching of the writes into
+the storage engine.
 
 Points in the WAL can be queried and persist through a system reboot.
-On process start, all points in the WAL must be flushed before the system accepts new writes.
+On process start, all points in the WAL must be flushed before the system
+accepts new writes.
 
 Related entries:
 [tsm](#tsm-time-structured-merge-tree)