More about RAM and IOPS

Author: jonels-msft

articles/postgresql/concepts-hyperscale-configuration-options.md

@@ -20,9 +20,7 @@ the logical CPU of the underlying hardware. The storage size for
 provisioning refers to the capacity available to the coordinator
 and worker nodes in your Hyperscale (Citus) server group. The storage
 includes  database files, temporary files, transaction logs, and
-the Postgres server logs. The total amount of storage you provision
-also defines the I/O capacity available to each worker and coordinator
-node.
+the Postgres server logs.
 
 |                       | Worker node           | Coordinator node      |
 |-----------------------|-----------------------|-----------------------|
@@ -32,6 +30,50 @@ node.
 | Storage type          | General purpose (SSD) | General purpose (SSD) |
 | IOPS                  | Up to 3 IOPS/GiB      | Up to 3 IOPS/GiB      |
 
+The total amount of RAM in a single Hyperscale (Citus) node is based on the
+selected number of vCores.
+
+| vCores | One worker node, GiB RAM | Coordinator node, GiB RAM |
+|--------|--------------------------|---------------------------|
+| 4      | 32                       | 16                        |
+| 8      | 64                       | 32                        |
+| 16     | 128                      | 64                        |
+| 32     | 256                      | 128                       |
+| 64     | 432                      | 256                       |
+
+The total amount of storage you provision also defines the I/O capacity
+available to each worker and coordinator node.
+
+| Storage size, TiB | Maximum IOPS |
+|-------------------|--------------|
+| 0.5               | 1,536        |
+| 1                 | 3,072        |
+| 2                 | 6,148        |
+
+For the entire Hyperscale (Citus) cluster, the aggregated IOPS work out to the
+following values:
+
+| Worker nodes | 0.5 TiB, total IOPS | 1 TiB, total IOPS | 2 TiB, total IOPS |
+|--------------|---------------------|-------------------|-------------------|
+| 2            | 3,072               | 6,144             | 12,296            |
+| 3            | 4,608               | 9,216             | 18,444            |
+| 4            | 6,144               | 12,288            | 24,592            |
+| 5            | 7,680               | 15,360            | 30,740            |
+| 6            | 9,216               | 18,432            | 36,888            |
+| 7            | 10,752              | 21,504            | 43,036            |
+| 8            | 12,288              | 24,576            | 49,184            |
+| 9            | 13,824              | 27,648            | 55,332            |
+| 10           | 15,360              | 30,720            | 61,480            |
+| 11           | 16,896              | 33,792            | 67,628            |
+| 12           | 18,432              | 36,864            | 73,776            |
+| 13           | 19,968              | 39,936            | 79,924            |
+| 14           | 21,504              | 43,008            | 86,072            |
+| 15           | 23,040              | 46,080            | 92,220            |
+| 16           | 24,576              | 49,152            | 98,368            |
+| 17           | 26,112              | 52,224            | 104,516           |
+| 18           | 27,648              | 55,296            | 110,664           |
+| 19           | 29,184              | 58,368            | 116,812           |
+| 20           | 30,720              | 61,440            | 122,960           |
 
 ## Regions
 Hyperscale (Citus) server groups are available in the following Azure regions: