Comment by arghwhat

> This example shows that the access.log file is being read at the speed of 37.4MB/s but gzip is writing data at only 1.74MB/s. We can immediately calculate the compression rate. It's 37.4/1.74 = 21x!

No you cannot:

1. Compression algorithms buffer a lot and will have have tendencies to perform large burst writes and in particular large writes on final flush. Instantaneous measurements will therefore not be particularly useful.

2. Compression ratio refers to the average across an entire file, as entropy is not uniform across the input unless you are compressing just noise or just zeros. Some sections might compress extremely well while others do not and end up consuming more space than the input due to overhead.