Azure Cosmos DB for PostgreSQL compute and storage
APPLIES TO:
Azure Cosmos DB for PostgreSQL (powered by the Citus database
extension to PostgreSQL)
Compute resources are provided as vCores, which represent 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 cluster. The storage includes database files, temporary files, transaction logs, and the Postgres server logs.
Multi-node cluster
You can select the compute and storage settings independently for worker nodes and the coordinator node in a multi-node cluster.
| Resource | Worker node | Coordinator node |
|---|---|---|
| Compute, vCores | 4, 8, 16, 32, 64, 96, 104 | 4, 8, 16, 32, 64, 96 |
| Memory per vCore, GiB | 8 | 4 |
| Storage size, TiB | 0.5, 1, 2, 4, 8, 16, 32 | 0.128, 0.25, 0.5, 1, 2, 4, 8, 16, 32 |
| Storage type | General purpose (SSD) | General purpose (SSD) |
The total amount of RAM in a single 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 | 512 | 256 |
| 96 | 672 | 384 |
| 104 | 672 | n/a |
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 | 2,300 |
| 1 | 5,000 |
| 2 | 7,500 |
| 4 | 7,500 |
| 8 | 16,000 |
| 16 | 18,000 |
| 32 | 20,000 |
For the entire cluster, the aggregated IOPS work out to the following values:
| Worker nodes | 0.5 TiB, total IOPS | 1 TiB, total IOPS | 2 or 4 TiB, total IOPS | 8 TiB, total IOPS | 16 TiB, total IOPS | 32 TiB, total IOPS |
|---|---|---|---|---|---|---|
| 2 | 4,600 | 10,000 | 15,000 | 32,000 | 36,000 | 40,000 |
| 3 | 6,900 | 15,000 | 22,500 | 48,000 | 54,000 | 60,000 |
| 4 | 9,200 | 20,000 | 30,000 | 64,000 | 72,000 | 80,000 |
| 5 | 11,500 | 25,000 | 37,500 | 80,000 | 90,000 | 100,000 |
| 6 | 13,800 | 30,000 | 45,000 | 96,000 | 108,000 | 120,000 |
| 7 | 16,100 | 35,000 | 52,500 | 112,000 | 126,000 | 140,000 |
| 8 | 18,400 | 40,000 | 60,000 | 128,000 | 144,000 | 160,000 |
| 9 | 20,700 | 45,000 | 67,500 | 144,000 | 162,000 | 180,000 |
| 10 | 23,000 | 50,000 | 75,000 | 160,000 | 180,000 | 200,000 |
| 11 | 25,300 | 55,000 | 82,500 | 176,000 | 198,000 | 220,000 |
| 12 | 27,600 | 60,000 | 90,000 | 192,000 | 216,000 | 240,000 |
| 13 | 29,900 | 65,000 | 97,500 | 208,000 | 234,000 | 260,000 |
| 14 | 32,200 | 70,000 | 105,000 | 224,000 | 252,000 | 280,000 |
| 15 | 34,500 | 75,000 | 112,500 | 240,000 | 270,000 | 300,000 |
| 16 | 36,800 | 80,000 | 120,000 | 256,000 | 288,000 | 320,000 |
| 17 | 39,100 | 85,000 | 127,500 | 272,000 | 306,000 | 340,000 |
| 18 | 41,400 | 90,000 | 135,000 | 288,000 | 324,000 | 360,000 |
| 19 | 43,700 | 95,000 | 142,500 | 304,000 | 342,000 | 380,000 |
| 20 | 46,000 | 100,000 | 150,000 | 320,000 | 360,000 | 400,000 |
Single node cluster
Single-node cluster resource options differ between burstable compute and regular compute.
Burstable compute
| Resource | Resource value |
|---|---|
| Burstable compute, vCores | 1, 2 |
| Burstable compute memory per vCore, GiB | 2 |
| Storage size, GiB (IOPS, up to) | 32 (120), 64 (240), 128 (500) |
| Storage type | General purpose (SSD) |
Regular compute
| Resource | Resource value |
|---|---|
| Compute, vCores | 2, 4, 8, 16, 32, 64 |
| Compute memory per vCore, GiB | 4 |
| Storage size, GiB (IOPS, up to) | 128 (500), 256 (1,100), 512 (2,300), 1024† (5,000), 2048† (7,500) |
| Storage type | General purpose (SSD) |
† 1024 GiB and 2048 GiB are supported with 8 vCores or greater.
Maximum IOPS for your compute / storage configuration
Each compute configuration has an IOPS limit that depends on the number of vCores in a node. Make sure you select compute configuration for the coordinator and worker nodes in your cluster to fully utilize IOPS in the selected storage.
Worker nodes, per node
| Compute | Storage size to maximize IOPS usage, up to | IOPS with the max recommended storage size, up to |
|---|---|---|
| 4 vCores | 1 TiB | 5,000 |
| 8 vCores | 4 TiB | 7,500 |
| 16 vCores | 32 TiB | 20,000 |
| 32 vCores | 32 TiB | 20,000 |
| 64 vCores | 32 TiB | 20,000 |
| 96 vCores | 32 TiB | 20,000 |
| 104 vCores | 32 TiB | 20,000 |
Coordinator and single node with regular compute
| Compute | Storage size to maximize IOPS usage, up to | IOPS with the max recommended storage size, up to |
|---|---|---|
| 2 vCores | 0.5 TiB | 2,300 |
| 4 vCores | 1 TiB | 5,000 |
| 8 vCores | 4 TiB | 7,500 |
| 16 vCores | 32 TiB | 20,000 |
| 32 vCores | 32 TiB | 20,000 |
| 64 vCores | 32 TiB | 20,000 |
| 96 vCores | 32 TiB | 20,000 |
To put it another way, if you need 8 TiB of storage per node or more, make sure you select 16 vCores or more for the node's compute configuration. That would allow you to maximize IOPS usage provided by the selected storage.
Next steps
- Learn how to create a cluster in the portal
- Change compute quotas for a subscription and region