SFTP Gateway Support

3.0

Database Instance Sizes

Overview

When deploying SFTP Gateway with a high availability (HA) configuration, we use an external PostgreSQL Flexible Server. By default, we use Standard_B1ms for the instance size.

For scenarios involving larger workloads, you want to use a larger database instance size (i.e. D2s_v3). Although it costs more, the D2s_v3 instance size supports more database connections, and can handle sustained traffic.

Background

In our kb for launching an HA ARM template, the default PostgreSQL database size is Standard_B1ms. While this works for most use cases, it becomes a bottleneck for larger workloads.

The issue may present itself as the VMs in the scale set reaching nearly 100% utilization. While at first it seems this is caused by heavy SFTP traffic, upon further inspection it's because the Java service on each VM is constantly failing. The specific Java errors indicate there is trouble reaching the database.

The Standard_B1ms database instance size only supports 50 connections. This can create a bottleneck for larger workloads, where VMs are unable to connect to the database.

Database instance sizes

Here are some database instance sizes, along with a few key metrics:

  • B1ms
    • 50 max connections
    • $15 / month
  • B2s
    • 429 max connections
    • $30 / month
  • B2ms
    • 859 max connections
    • $60 / month
  • D2s_v3
    • 859 max connections
    • $70 / month

If your troubleshooting indicates that the database max connections is a bottleneck, consider upgrading your database instance size to at least a B2s.

If you have a heavy workload and need reliable performance, consider upgrading to at least a D2s_v3.

Editing the ARM template

In the ARM template, the PostgreSQL resource is found under this object:

"type": "Microsoft.DBforPostgreSQL/flexibleServers"

In the object properties, the sku defines the database instance size:

"sku": {
  "name": "Standard_B1ms",
  "tier": "Burstable"
},

The B class uses the Burstable tier. If you want to use a D class, you need to use the GeneralPurpose tier:

"sku": {
  "name": "D2s_v3",
  "tier": "GeneralPurpose"
},
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