User GuideNIXL Backends

Azure Blob

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Overview

The Azure Blob backend enables DRAM-to-object-storage transfers using the Azure Blob REST API for workloads in Azure cloud environments.

PropertyValue
Transfer TypeDRAM ↔ Object
ProtocolAzure Blob REST API
Best ForAzure cloud deployments with Blob Storage

Installation

The Azure Blob backend requires the azure-storage-blobs and azure-identity packages from azure-sdk-for-cpp.

Build from Source

git clone --depth 1 https://github.com/Azure/azure-sdk-for-cpp.git \
    --branch azure-storage-blobs_12.15.0
cd azure-sdk-for-cpp/
mkdir build && cd build
AZURE_SDK_DISABLE_AUTO_VCPKG=1 cmake .. \
    -DCMAKE_BUILD_TYPE=Release \
    -DBUILD_SHARED_LIBS=ON \
    -DCMAKE_INSTALL_PREFIX=/usr/local \
    -DDISABLE_AMQP=ON \
    -DDISABLE_AZURE_CORE_OPENTELEMETRY=ON
cmake --build . --target azure-storage-blobs azure-identity
cmake --install sdk/core
cmake --install sdk/storage/azure-storage-common
cmake --install sdk/storage/azure-storage-blobs
cmake --install sdk/identity

After installing the Azure SDK, rebuild NIXL to enable the Azure Blob backend.

Configuration

Environment Variables

VariableTypeDefaultDescription
AZURE_STORAGE_ACCOUNT_URLString (URL)NoneAzure Storage account URL (e.g., https://<account>.blob.core.windows.net).
AZURE_STORAGE_CONTAINER_NAMEStringNone (required)Azure Storage container name for blob operations.
AZURE_STORAGE_CONNECTION_STRINGStringNoneAzure Storage connection string. Used for local development with Azurite or when connection string auth is preferred.
AZURE_CA_BUNDLEString (path)NoneCustom CA certificate bundle path for Azure HTTPS connections.

Backend parameters passed to createBackend() take precedence over these environment variables. Supported override keys are account_url, container_name, connection_string, and ca_bundle.

When to Use

  • Azure cloud storage — Deployments where Blob Storage is the target object store.
  • Checkpoint workflows — Save and load model checkpoints on Azure infrastructure.
  • Azure-native object storage — Use this backend for Azure Blob; use OBJ for S3-compatible storage.