Could you kindly tell me what is persistent grades feature exactly?
why is it disabled by default? and is it safe to enable it for a site with 20K learners or not?
is there any documents about it? (unfortunately I didn’t find anything by googling.)
thank you very much
By default, grades in Open edX are computed on the fly and are not stored in the database. This can make it slow/expensive to do things like produce reports of grades for a large course. Enabling persistent grades causes the grades to be stored in the database (MySQL), which makes a lot of grade-related reporting much faster because the grades can simply be read out of the database instead of computed for each student/course/subsection.
I am also curious about why the persistent grades feature is still disabled by default and why the “non persistent” grades mode still exists at all. Would someone from edX be able to comment on that?
For what it’s worth, we have been using persistent grades for several of our Open edX installations of various size for several years without any issues that I’m aware of. I recommend enabling it if you’re using the Ironwood release of Open edX or newer (earlier releases are known to have some related bugs).