FOSS gamedev and creative worlds

It seems every player file is re-written when the player data is saved. All of my player files have the same modified date/time. There are currently 11,927 player files on my server, I have to think that writing all of these player files has a negative impact on performance. Can it be changed so only online players files are updated, or is there a reason all player files have to be re-written?

I agree this happened to be what made 0gb.us's server way too laggy.

This should be actually be fixed, but it seems that it isnt working correctly.
More precisely: the inventory is always seen as modified, because either the = or == operator on Inventory or InventoryList is buggy.