I have a table which consists of heavy blobs, and I wanted to conduct some tests on it.

I know deleted space is not reclaimed by innodb, so I decided to reuse existing records by updating its own values instead of createing new records.

But I noticed, whether I delete and insert a new entry, or I do UPDATE on existing ROW, InnoDB keeps on growing. 

Assuming I have 100 Rows, each Storing 500KB of information, My InnoDB size is 10MB, now when I call UPDATE on all rows (no insert/ no delete), the innodb grows by ~8MB for every run I do. All I am doing is I am storing exactly 500KB of data in each row, with little modification, and size of blob is fixed.

What can I do to prevent this?

I know about optimize table, but I cant do it because on regular usage, the table is going to be 60-100GB big, and running optimize will just stall entire server.