They have yearly expenses for more than $500.000
https://docs.google.com/spreadsheets/d/1Si3PMUJGR9KrpE5lngSk...
Seems really weird to be using harddrives when they already have expenses like that.
Source: am président of the lichess charity (and also one of the sysadmins)
And while 500k is a lot maybe they can do so much with it because they do not just throw $1500 in drives at every problem.
"WDL tables (.rtbw) store the outcome of positions, e.g. if a position is winning. An engine will use this very frequently to decide which endgames to aim for. WDL tables should be stored on the fastest disk (preferably SSD) you have." "DTZ tables (.rtbz) tell the engine how to finish the endgame once it is on the board. They are optional, but required to reliably convert complicated endings."
Seems reasonable to put the WDL table on the SSD for better engine performance. I do understand not choosing SSD's. The number of lookups for positions always remains the same per user per game. Yet the tablebase is growing more than exponentially.
https://lichess.org/@/lichess/blog/7-piece-syzygy-tablebases...