Move attachments from database to file system

[skariko]

Hello, i'm wondering what exactly the option "move attachments from database to disk" does ? I mean, it's something that works "from now on", or it will migrate all my pre-existing attachments (300MB by far). Would be a risky thing to move all my attachments to filesystem ? I tend to believe it will improve the performance of my forum because an apache hit is "lighter" than a mysql hit ,but i'm quite doubtful to change something that works. So i'm wondering if should i do something before, if it's a risky thing, and such.

Thank you very much, have a nice day
Bye