SMB (Server Message Block) signing enhances data integrity by ensuring that each SMB message is authenticated, thereby protecting against man-in-the-middle attacks and replay attacks. However, this security measure introduces additional processing overhead, impacting CPU usage on both client and server sides.
Impact on Client and Server CPU Usage
When SMB signing is enabled, both clients and servers experience increased CPU utilization due to the cryptographic operations required to sign and verify each SMB message. This overhead is particularly noticeable during high-throughput operations or when handling numerous SMB sessions. For instance, enabling SMB signing has been observed to reduce throughput from approximately 875 MiB/s to around 250 MiB/s during sequential read tests without multichannel support.
Factors Influencing Performance Impact
The extent of the performance degradation depends on several factors:
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Hardware Capabilities: Systems equipped with AES-NI (Advanced Encryption Standard New Instructions) can offload cryptographic operations, mitigating the performance impact.
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SMB Version: Newer versions of SMB, such as SMB 3.1.1, offer improved signing algorithms like AES-128-GMAC, which provide better performance and security compared to older versions.
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Network Environment: The volume of SMB traffic and the number of concurrent sessions can affect the overall performance impact.
Mitigating Performance Degradation
To minimize the performance overhead associated with SMB signing:
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Use Hardware with AES-NI Support: Deploy systems that support AES-NI to offload cryptographic operations and reduce CPU load.
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Upgrade to SMB 3.1.1: Utilize the latest SMB protocol versions that incorporate more efficient signing algorithms.
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Optimize Network Configuration: Implement features like SMB Multichannel to distribute traffic across multiple network paths, enhancing throughput.
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Conduct Performance Baselines: Regularly assess system performance to understand the impact of SMB signing and make informed decisions about its configuration.
While SMB signing introduces additional CPU overhead, its security benefits often outweigh the performance trade-offs, especially in environments where data integrity is paramount.
