I see in log file such strings all the time:
Flushing wallet.dat 9433ms
Flushing wallet.dat 13237ms
If I use "top" command I see
6.3 us, 2.4 sy, 6.0 ni, 23.7 id, 61.6 wa
61.6% waiting of I/O it's a lot, so disk is really overloaded.
This can be reason of slow work and how to resolve the problem? To have separate disk/server for every coin?

command "iotop" that shows I/O waiting processes shows me that CrocodileCashD and QubitCoinD - 2 coins with 30 seconds block time (Croc even worse since it has PoS), so no idea what to do with that coins
For now I'm going to delist qubit coin
Searching in internet give me no solution. Actually it is not a common thing when PoW, PoS and deposits (addresses generating) work on the same wallet