Change default parallelism of Storage SDK (#7190)

Author: Jinming-Hu

sdk/storage/azure-storage-blobs/CHANGELOG.md

@@ -10,6 +10,8 @@
 
 ### Other Changes
 
+- Updated the default concurrency for upload and download operations. It now scales with the number of hardware threads available, clamped between 8 and 96 (previously a fixed value of 5).
+
 ## 12.18.0 (2026-06-11)
 
 ### Features Added

sdk/storage/azure-storage-blobs/inc/azure/storage/blobs/blob_options.hpp

@@ -11,7 +11,9 @@
 #include <azure/core/modified_conditions.hpp>
 #include <azure/storage/common/access_conditions.hpp>
 #include <azure/storage/common/crypt.hpp>
+#include <azure/storage/common/internal/concurrent_transfer.hpp>
 
+#include <algorithm>
 #include <chrono>
 #include <cstdint>
 #include <memory>
@@ -776,7 +778,7 @@ namespace Azure { namespace Storage { namespace Blobs {
       /**
        * @brief The maximum number of threads that may be used in a parallel transfer.
        */
-      int32_t Concurrency = 5;
+      int32_t Concurrency = (std::min)(96, (std::max)(8, _internal::GetHardwareConcurrency()));
     } TransferOptions;
 
     /**
@@ -1023,7 +1025,7 @@ namespace Azure { namespace Storage { namespace Blobs {
       /**
        * @brief The maximum number of threads that may be used in a parallel transfer.
        */
-      int32_t Concurrency = 5;
+      int32_t Concurrency = (std::min)(96, (std::max)(8, _internal::GetHardwareConcurrency()));
     } TransferOptions;
 
     /**

sdk/storage/azure-storage-common/CMakeLists.txt

@@ -70,6 +70,7 @@ set(
 set(
   AZURE_STORAGE_COMMON_SOURCE
     src/account_sas_builder.cpp
+    src/concurrent_transfer.cpp
     src/crypt.cpp
     src/file_io.cpp
     src/private/package_version.hpp

sdk/storage/azure-storage-common/inc/azure/storage/common/internal/concurrent_transfer.hpp

@@ -13,6 +13,8 @@
 
 namespace Azure { namespace Storage { namespace _internal {
 
+  int GetHardwareConcurrency();
+
   inline void ConcurrentTransfer(
       int64_t offset,
       int64_t length,

sdk/storage/azure-storage-common/src/concurrent_transfer.cpp

@@ -0,0 +1,16 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+#include "azure/storage/common/internal/concurrent_transfer.hpp"
+
+#include <thread>
+
+namespace Azure { namespace Storage { namespace _internal {
+
+  int GetHardwareConcurrency()
+  {
+    static int c = static_cast<int>(std::thread::hardware_concurrency());
+    return c;
+  }
+
+}}} // namespace Azure::Storage::_internal

sdk/storage/azure-storage-files-datalake/CHANGELOG.md

@@ -10,6 +10,8 @@
 
 ### Other Changes
 
+- Updated the default concurrency for upload and download operations. It now scales with the number of hardware threads available, clamped between 8 and 96 (previously a fixed value of 5).
+
 ## 12.16.0 (2026-06-11)
 
 ### Features Added

sdk/storage/azure-storage-files-datalake/inc/azure/storage/files/datalake/datalake_options.hpp

@@ -9,7 +9,9 @@
 #include <azure/core/nullable.hpp>
 #include <azure/storage/blobs/blob_options.hpp>
 #include <azure/storage/common/access_conditions.hpp>
+#include <azure/storage/common/internal/concurrent_transfer.hpp>
 
+#include <algorithm>
 #include <cstdint>
 #include <memory>
 #include <string>
@@ -1040,7 +1042,7 @@ namespace Azure { namespace Storage { namespace Files { namespace DataLake {
       /**
        * The maximum number of threads that may be used in a parallel transfer.
        */
-      int32_t Concurrency = 5;
+      int32_t Concurrency = (std::min)(96, (std::max)(8, _internal::GetHardwareConcurrency()));
     } TransferOptions;
 
     /**

sdk/storage/azure-storage-files-shares/CHANGELOG.md

@@ -10,6 +10,8 @@
 
 ### Other Changes
 
+- Updated the default concurrency for upload and download operations. It now scales with the number of hardware threads available, clamped between 8 and 96 (previously a fixed value of 5).
+
 ## 12.18.0 (2026-06-11)
 
 ### Features Added

sdk/storage/azure-storage-files-shares/inc/azure/storage/files/shares/share_options.hpp

@@ -9,7 +9,9 @@
 #include <azure/core/internal/extendable_enumeration.hpp>
 #include <azure/core/nullable.hpp>
 #include <azure/storage/common/access_conditions.hpp>
+#include <azure/storage/common/internal/concurrent_transfer.hpp>
 
+#include <algorithm>
 #include <memory>
 #include <string>
 #include <vector>
@@ -1353,7 +1355,7 @@ namespace Azure { namespace Storage { namespace Files { namespace Shares {
       /**
        * The maximum number of threads that may be used in a parallel transfer.
        */
-      int32_t Concurrency = 5;
+      int32_t Concurrency = (std::min)(96, (std::max)(8, _internal::GetHardwareConcurrency()));
     } TransferOptions;
   };
 
@@ -1422,7 +1424,7 @@ namespace Azure { namespace Storage { namespace Files { namespace Shares {
       /**
        * The maximum number of threads that may be used in a parallel transfer.
        */
-      int32_t Concurrency = 5;
+      int32_t Concurrency = (std::min)(96, (std::max)(8, _internal::GetHardwareConcurrency()));
     } TransferOptions;
   };