What happened if I run two similar nodes with the same wallet.dat and run PoS mining on both? I want to do it in case of crashed of one of the wallet and PoS wont stop
You can run into problems if they are buying tickets, as they may use addresses the other one isn't checking. You then need to delete the wallet and recreate from seed to get them synced. If you use --reuseaddresses on your wallet, or --ticketaddress to assign voting rights to a known address it seems to work OK. The best practise is to use --ticketaddress to assign voting rights to a "hot" wallet, which has no funds of it's own. You can then have multiple copies of the "hot" wallet online and voting and everything is fine, as they aren't making transactions or generating addresses.