Storage in Azure Database for PostgreSQL flexible server

APPLIES TO: Azure Database for PostgreSQL - Flexible Server

You can create an Azure Database for PostgreSQL flexible server instance using Azure managed disks, which are block-level storage volumes managed by Azure and used with Azure Virtual Machines. Managed disks are like a physical disk in an on-premises server, but they're virtualized. With managed disks, all you have to do is specify the disk size, the disk type, and provision the disk. Once you provision the disk, Azure handles the rest. Azure Database for PostgreSQL flexible server supports premium solid-state drives (Premium SSD) and premium solid-state drives version 2 (Premium SSD v2), and the pricing is calculated based on the compute, memory, and storage tier you provision.

Premium SSD

Azure Premium SSD deliver high-performance and low-latency disk support for virtual machines (VMs) with input/output (IO)-intensive workloads. Premium SSD units are suitable for mission-critical production applications.

Premium SSD v2 (preview)

Premium SSD v2 offers higher performance than Premium SSD, while also being less costly, as a general rule. You can individually tweak the performance (capacity, throughput, and input/output operations per second, referred to as IOPS) of Premium SSD v2 at any time. The ability to do these adjustments allow workloads to be cost-efficient, while meeting shifting performance needs. For example, a transaction-intensive database might need to cope with a large amount of IOPS for a couple of exceptionally high-demand days. Or a gaming application might demand higher throughput during peak hours only. Hence, for most general-purpose workloads, Premium SSD v2 can provide the best price for performance. You can now deploy Azure Database for PostgreSQL flexible server instances with Premium SSD v2 disk in all supported regions.

Differences between Premium SSD and Premium SSD v2

Unlike Premium SSD, Premium SSD v2 doesn't have dedicated sizes. You can set a Premium SSD v2 disk to any size you prefer, and make granular adjustments as per your workload requirements. Those granular increments can go in steps of 1 GiB. Premium SSD v2 doesn't support host caching, but still provide lower latency than Premium SSD. Premium SSD v2 capacities range from 1 GiB to 64 TiBs.

The following table provides a comparison of different aspect of the types of disk supported by Azure Database for PostgreSQL flexible server, to help you decide which one suits your needs better.

Premium SSD v2 offers up to 32 TiBs per region per subscription by default, but supports higher capacity by request. To request an increase in capacity, request a quota increase or contact Azure Support.

Azure Database for PostgreSQL flexible server offers a baseline throughput of 125 MB/s for disks up to 399 GiB, and 500 MB/s for disks over 400 GiB at no extra cost. Increasing throughput beyond the free tier results in extra charges.

The storage that you provision is the amount of storage capacity available to your Azure Database for PostgreSQL flexible server instance. This storage is used for database files, temporary files, transaction logs, and PostgreSQL server logs. The total amount of storage that you provision also defines the I/O capacity available to your server.

The following table provides an overview of premium SSD v2 disk capacities and performance maximums to help you decide which want you should use.

Your virtual machine type also has IOPS limits. Although you can select any storage size, independently from the server type, you might not be able to use all IOPS that the storage provides, especially when you choose a server with a few vCores. To learn more, see compute options in Azure Database for PostgreSQL flexible server.

You can monitor your I/O consumption in the Azure portal, or by using Azure CLI commands. The relevant metrics to monitor are storage limit, storage percentage, storage used, and I/O percentage.

Disk full conditions

When your disk becomes full, the server starts returning errors and prevents any further modifications. Reaching the limit might also cause problems with other operational activities, such as backups and write-ahead log (WAL) archiving. There are different ways with which this disk full condition can be avoided:

• To avoid this situation, the server is automatically switched to read-only mode when the storage usage reaches 95 percent, or when the available capacity is less than 5 GiB. If you're using Premium SSD storage type, you can use the storage autogrow feature or scale up the storage of the server to avoid this issue from occurring.
• If the server is marked as read only because of disk full condition, you can delete the data that is no longer required. To do this, you can execute the below command to change the mode to read-write, and once that is done, you can execute delete command.

	SET SESSION CHARACTERISTICS AS TRANSACTION READ WRITE;

We recommend that you actively monitor the disk space that's in use by using storage_percentage or storage_used metrics and increase the disk size before you run out of available space in your storage. You can set up an alert to notify you when your server storage is approaching an out-of-disk state. For more information, see how to use the Azure portal to set up alerts on metrics for Azure Database for PostgreSQL flexible server.

Price

For the most up-to-date pricing information, see Azure Database for PostgreSQL flexible server pricing.

Azure portal also shows you an estimation of the monthly costs of a server configuration, based on the options selected.

That estimation can be seen throughout the server creation experience, in the New Azure Database for PostgreSQL Flexible server page:

It can also be seen for existing servers if, in the resource menu of an existing instance, under the Settings section, you select Compute + storage:

If you don't have an Azure subscription, you can use the Azure pricing calculator to get an estimated price. In the Azure pricing calculator website, select Databases category, and then select Azure Database for PostgreSQL to add the service to your estimate and then customize the options.

Related content

• Manage Azure Database for PostgreSQL flexible server.
• Limits in Azure Database for PostgreSQL flexible server.