How to use rpk to analyze partitions and size clusters

modules/deploy/pages/deployment-option/self-hosted/manual/sizing.adoc

@@ -153,6 +153,89 @@ The https://github.com/redpanda-data/openmessaging-benchmark[Open Messaging Benc
 
 See also: https://github.com/redpanda-data/openmessaging-benchmark/blob/main/driver-redpanda/README.md[Redpanda Benchmarks^]
 
+== Assess throughput
+
+This section describes how to use the xref:reference:rpk/rpk-topic-analyze.adoc[`rpk topic analyze`] command to check how much work your Redpanda cluster is handling. It shows the number of messages the cluster is processing and the size of the data groups (batches). This information helps you decide if you need to add more servers or make changes to your setup.
+
+This command shows you the throughput of your Redpanda cluster:
+
+[source,bash]
+----
+rpk topic analyze --regex '*' --print-all --time-range -1m:end
+----
+
+The arguments are:
+
+* `--regex '*'`: Analyzes all topics.
+* `--print-all`: Prints all the metrics.
+* `--time-range -1m:end`: Analyzes the last minute of data.
+
+Example output:
+
+[,bash,role="no-copy no-wrap"]
+----
+SUMMARY
+=======
+TOPICS                        6
+PARTITIONS                    17
+TOTAL THROUGHPUT (BYTES/S)    1361.9166666666667
+TOTAL BATCH RATE (BATCHES/S)  2.9833333333333334
+AVERAGE BATCH SIZE (BYTES)    456.50837988826817
+
+TOPIC SUMMARY
+=============
+TOPIC                     PARTITIONS  BYTES-PER-SECOND    BATCHES-PER-SECOND  AVERAGE-BYTES-PER-BATCH
+_redpanda.audit_log       12          61                  0.1                 610
+_redpanda.transform_logs  1           890.2666666666667   0.7833333333333333  1136.5106382978724
+_schemas                  1           0                   0                   0
+edu-filtered-domains      1           14.283333333333333  0.1                 142.83333333333334
+logins                    1           144.61666666666667  1                   144.61666666666667
+transactions              1           251.75              1                   251.75
+
+PARTITION BATCH RATE (BATCHES/S)
+================================
+TOPIC                     P25                   P50                   P75                  P99
+_redpanda.audit_log       0.016666666666666666  0.016666666666666666  0.03333333333333333  0.03333333333333333
+_redpanda.transform_logs  0.7833333333333333    0.7833333333333333    0.7833333333333333   0.7833333333333333
+_schemas                  0                     0                     0                    0
+edu-filtered-domains      0.1                   0.1                   0.1                  0.1
+logins                    1                     1                     1                    1
+transactions              1                     1                     1                    1
+
+PARTITION BATCH SIZE (BYTES)
+============================
+TOPIC                     P25   P50   P75   P99
+_redpanda.audit_log       608   610   610   611
+_redpanda.transform_logs  895   895   895   895
+_schemas                  0     0     0     0
+edu-filtered-domains      141   141   141   141
+logins                    144   144   144   144
+transactions              255   255   255   255
+----
+
+* **Total throughput:**
+  Indicates the total amount of data processed by the cluster every second.
+
+* **Total batch rate:**
+  Shows the number of message batches processed per second. A higher rate suggests increased activity, which may require more CPU or I/O resources.
+
+* **Average batch size:**
+  Reflects the average size of each message batch. Large or inconsistent batch sizes may indicate the need to adjust producer settings or verify storage capacity.
+
+* **Topic and partition summaries:**
+  Provides details on resource usage by individual topics. For example, if a single topic (such as `_redpanda.transform_logs` in the example output) is responsible for most throughput, it may need optimization or additional resources.
+
+* **Percentiles (P25, P50, P75, P99):**
+  Offers insights into workload distribution across partitions. Consistent values suggest balanced workloads, while significant variations may highlight areas that need rebalancing or capacity adjustments.
+
+=== Plan for capacity
+
+Compare the current throughput and batch rate with your cluster's hardware limits, such as network bandwidth, disk IOPS, or CPU capacity. If usage is nearing these limits, consider scaling up (upgrading hardware) or scaling out (adding brokers). Monitor trends over time to anticipate when expansion is necessary.
+
+=== Address bottlenecks
+
+If specific topics or partitions consistently show higher loads, it may indicate uneven workload distribution. Redistribute partitions or adjust replication factors to balance the load more effectively.
+
 include::shared:partial$suggested-reading.adoc[]
 
 * https://redpanda.com/blog/sizing-redpanda-cluster-best-practices[Four sizing principles for Redpanda production clusters^]