Improve SMB Azure File Share Performance

Here’s a concise, GitBook-ready summary of the article, plus the SMB Multichannel verification steps converted into a stepper.

Summary

• Scope: How to improve performance for SSD (premium) SMB Azure file shares (including SMB Multichannel).

• Key optimization tips:

  • Keep the storage account and client in the same Azure region to reduce latency.

  • Use multi-threaded applications and spread work across multiple files.

  • SMB Multichannel benefits increase with number of files and parallelism.

  • SSD share performance is bounded by provisioned share size (IOPS, throughput) and single-file limits. See: https://docs.azure.cn/en-us/storage/files/understand-performance and https://docs.azure.cn/en-us/storage/files/understanding-billing#provisioned-v1-model

  • A single VM client is still limited by VM network/CPU/storage limits (example: Standard_D32s_v3 ~1.86 GiB/s). Reads (ingress) are not egress-metered; writes are.

  • Warm up tests and repeat; if one client is the bottleneck, spread load across multiple clients.

Throughput / IOPS relationship

• Throughput = IO size * IOPS.

• Larger IO sizes → higher throughput but higher latency and fewer net IOPS.

• Smaller IO sizes → higher IOPS but lower throughput.

SMB Multichannel — overview

• Enables an SMB client to open multiple network connections to an SMB file share.

• Supported on SSD file shares for Windows clients.

• Enabled by default on the service for newly created storage accounts in all regions; no extra cost.

SMB Multichannel — benefits

• Increased throughput by aggregating multiple network paths (helps large I/O workloads).

• Higher IOPS via NIC RSS distributing load across CPUs (helps small-I/O workloads).

• Network fault tolerance via multiple connections.

• Automatic/dynamic configuration when enabled on both client and service.

• Potential cost optimization by reducing number of VMs needed for a workload.

SMB Multichannel — limitations

• Only for SSD file shares (not HDD).

• Requires SMB 3.1.1 clients with recommended patches.

• Maximum of four channels per connection: see https://learn.microsoft.com/troubleshoot/azure/azure-storage/files-troubleshoot-performance?toc=/storage/files/toc.json#cause-4-number-of-smb-channels-exceeds-four

Configuration and verification

• SMB Multichannel must be enabled on both client and service.

• On Windows clients, it is enabled by default. Check client setting:

  • Get-SmbClientConfiguration | Select-Object -Property EnableMultichannel

• Check service status: https://docs.azure.cn/en-us/storage/files/files-smb-protocol#smb-multichannel

Verify SMB Multichannel is configured correctly (stepper)

1

Create or choose an SSD file share

Create a new SSD file share or use an existing SSD file share.

2

Ensure client supports SMB Multichannel

Confirm your client has one or more network adapters with receive-side scaling (RSS) enabled. See Windows docs: https://docs.azure.cn/en-us/azure-stack/hci/manage/manage-smb-multichannel

3

Mount the file share

Mount the SSD file share to your client machine.

4

Generate load

Run your application or a tool (for example robocopy /MT, Diskspd) to generate read/write load.

5

Inspect SMB Multichannel connections

Open PowerShell as admin and run: Get-SmbMultichannelConnection | fl

6

Check channel properties

Look for MaxChannels and CurrentChannels properties to verify active channels.

Performance comparison (summary)

• Multi-threaded / multiple files: Significant improvements (2x–4x) in IOPS and throughput; SMB Multichannel recommended.

• Multi-threaded / single file: Benefits usually when average I/O size >16 KiB; small I/Os may see ~10% regression — consider spreading across files or disabling feature.

• Single-threaded (single or multiple files): Little or negative benefit (≈10% degradation); typically disable unless workload can use multiple files and larger IOs.

Test notes & example

• Test config used: Standard D32s v3 VM, single RSS-enabled NIC, four channels; diskspd.exe with multiple threads and IO depth 10.

• Example diskspd command used in testing: diskspd.exe -W300 -C5 -r -w100 -b4k -t8 -o8 -Sh -d60 -L -c2G -Z1G z:\write0.dat z:\write1.dat ... z:\write9.dat

References / Next steps

• Check SMB Multichannel status: https://docs.azure.cn/en-us/storage/files/files-smb-protocol#smb-multichannel

• Windows SMB Multichannel docs: https://docs.azure.cn/en-us/azure-stack/hci/manage/manage-smb-multichannel

Last updated in source: 11/11/2025

If you’d like, I can also:

• Produce a one-page checklist (printable) of optimization actions.

• Create a troubleshooting expandable section for common SMB Multichannel issues.