You could only keep the detail in memory for a particular window of time. For example, keep a rolling window of two or three hours of trace logging in memory.

You could only keep the detail in memory for a particular window of time. For example, keep a rolling window of two or three hours of trace logging in memory. If the number of errors in that window passes a threshold, write the full trace out to disk, otherwise just write the info logging. You save on disk space while having detailed logging around errors.