Is there a good reason to store big text data outside database?
You might want to consider moving the data outside the database if:


You are having problems with backup durations
It causes disk or network throughput problems on your database server
You have a requirement to access the data without using the database


In general, I'd suggest keeping it in the database unless you can come up with a good reason not to.

There's some overlap between this question and "Files - in the database or not?". You might find some useful thoughts there, though things that are true for binary files don't necessarily hold true for text data.

MySQL offers some useful features where text is stored in the database, such as opportunities to use full-text indexing, and network compression.