Change default parallelism of Storage SDK#7008
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Pull request overview
Updates Azure Storage C++ transfer defaults to better match modern hardware by basing parallelism on CPU count and increasing default chunk/block sizes, aligning with #7007.
Changes:
- Increase default download chunk size to 16 MiB (Blobs, Files Shares; DataLake via Blob option aliasing).
- Change default transfer parallelism to be CPU-based (upload: CPU count; download: CPU/2 with a minimum of 1).
- Add
_internal::GetHardwareConcurrency()helper in azure-storage-common and wire it into option defaults.
Reviewed changes
Copilot reviewed 7 out of 7 changed files in this pull request and generated 6 comments.
Show a summary per file
| File | Description |
|---|---|
| sdk/storage/azure-storage-files-shares/inc/azure/storage/files/shares/share_options.hpp | Update download chunk size default and compute CPU-based concurrency defaults. |
| sdk/storage/azure-storage-files-datalake/inc/azure/storage/files/datalake/datalake_options.hpp | Update upload concurrency default to use CPU count via shared helper. |
| sdk/storage/azure-storage-common/src/concurrent_transfer.cpp | Add cached hardware concurrency helper implementation. |
| sdk/storage/azure-storage-common/inc/azure/storage/common/internal/concurrent_transfer.hpp | Declare hardware concurrency helper (used by option defaults). |
| sdk/storage/azure-storage-common/CMakeLists.txt | Add new source file to the common library build. |
| sdk/storage/azure-storage-blobs/src/block_blob_client.cpp | Increase default minimum stage block size to 16 MiB for uploads. |
| sdk/storage/azure-storage-blobs/inc/azure/storage/blobs/blob_options.hpp | Update download chunk size default and compute CPU-based concurrency defaults. |
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still under discussion. |
antkmsft
approved these changes
May 19, 2026
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wait until after STG 102 GA release |
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closes #7007
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