: For maximum efficiency, the solid block size should be at least as large as the total size of the input data. For example, if you have 8GB of files, a 32GB solid block size ensures the best results on 64-bit systems.
Solid compression is most effective when you are archiving a large number of very similar files, such as multiple versions of a document or software backups. Instead of compressing each file individually, 7-Zip looks for redundancies across all files in the "solid block." Elle.7z
7-Zip / Discussion / Help: 7-zIp And Compression Noob - SourceForge : For maximum efficiency, the solid block size
: It achieves a much smaller total file size than standard compression because it can reference identical data across different files. Instead of compressing each file individually, 7-Zip looks
: Reducing the dictionary size can help if you are low on RAM, but it will generally result in a larger file. Best Use Cases
: Best for files you don't need to access frequently, as individual file extraction is slower than in non-solid archives.
: Increasing the number of threads to match your CPU's logical processors can speed up the compression process, though it may slightly increase the final archive size.