How does iSCSI compare to Samba (SMB) in performance on my NAS?
Applicable products
- TS-462A with QTS 5.2.6.3170 Build 20250620
Overview
iSCSI and Samba (SMB/CIFS) are two protocols for accessing storage on a QNAP NAS. iSCSI provides block-level access, allowing the NAS to appear as a local disk to the connected computer, while Samba offers file-level network sharing, enabling multiple users to access folders over the network. Performance can vary depending on the access protocol, file size, and workload.
Analysis
A benchmark was performed on a QNAP TS-462A running over a 2.5GbE network. The results below compare iSCSI and SMB performance for large and small file transfers.
Large file transfers (32GB x 1 single file)
- SMB: Upload: 295 MB/s | Download: 296 MB/s
- iSCSI: Upload: 266 MB/s | Download: 265 MB/s
- Result: SMB was approximately 11–12% faster than iSCSI for large file transfers.
Small file transfers (1MB x 32,768 files)
- SMB: Upload: 98.5 MB/s | Download: 119 MB/s
- iSCSI: Upload: 293 MB/s | Download: 167 MB/s
- Result: For small file transfers, SMB was approximately 29% to 66% slower than iSCSI.
Actual performance may vary depending on NAS hardware, network setup, and configuration. These results are from one configuration (TS-462A, QTS 5.2.6.3170 Build 20250620, 2.5GbE).
Recommendation
For most users, Samba (SMB) is recommended for cross-platform file sharing as it is widely supported by Windows, macOS, and Linux. SMB is generally faster for large file transfers and best suited for multi-user or cross-system environments.
iSCSI can provide higher performance for small file transfers and is ideal when a single computer requires block-level access, such as for virtualization or databases. If your use case involves optimizing small file transfer performance to a single device, consider iSCSI.
Overall, SMB remains the preferred choice for most scenarios.
