How do you measure and optimize the performance impact of encryption on your stored procedures?

1 Encryption Options in SQL Server

SQL Server offers several encryption options for different levels of data protection and performance, such as Transparent Data Encryption (TDE), Column-level Encryption, and Always Encrypted. TDE encrypts the entire database at the file level without requiring any changes to the application or stored procedures, but it also has a high level of overhead. Column-level Encryption encrypts specific columns of data within a table using symmetric or asymmetric keys, but requires more coding and maintenance. Always Encrypted encrypts the data at the client side using a certificate or HSM and prevents the data from being exposed to the SQL Server, however, it also limits operations that can be performed on the encrypted data.

2 Measuring Encryption Overhead

To measure the performance impact of encryption on your stored procedures, you must compare the execution time, CPU usage, memory usage, and I/O activity of the encrypted and unencrypted versions of your database and stored procedures. SQL Server Profiler is a graphical tool that can be used to capture duration, CPU, reads, writes, and other statistics of your stored procedures before and after encryption. Extended Events is also a viable option for collecting and processing data about the activity and performance of your SQL Server instance. You can create sessions that capture events related to encryption errors, key operations, or algorithms used. Lastly, Dynamic Management Views (DMVs) can be used to query various aspects of your encryption configuration and performance such as encryption state, scan status, or IO stall.

3 Optimizing Encryption Performance

To optimize the performance of your stored procedures while using encryption, you should consider several factors and apply some best practices. The right encryption option should be chosen based on security requirements and performance expectations. For instance, if you need to encrypt the whole database, TDE may be used, but with a high overhead. If you need to encrypt only some columns and can afford to change your stored procedures, column-level encryption should be used with the appropriate keys and algorithms. Additionally, Always Encrypted may be used if you need to encrypt the data at the client side and do not need to perform complex operations on the encrypted data. Moreover, your stored procedures should be well-written and optimized for performance. This includes avoiding unnecessary or inefficient queries, using proper indexes and statistics, avoiding cursors and loops, using parameterized queries and sp_executesql, and avoiding recompilations and plan cache bloat. Furthermore, your encryption should be monitored and tested regularly to ensure it does not cause unexpected issues or degrade performance over time. This means checking for any errors or warnings related to encryption, measuring the encryption overhead and comparing it to your baseline or expectations, and testing backup and restore procedures as well as disaster recovery scenarios.

4 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?