I'm sure there are major backups to all such computer systems, though others are much more knowledgeable about that than I am.
People think about it more these days, now that everyone's fairly computer-savvy and we're all very aware that one's bank account is more pixels than cold hard cash. But really, a bank account was always only as good as the records being kept. Was it more reassuring when all such records were handwritten in ledger books instead of being entered into a computer system that's backed up (hopefully) at least every night?
Anyway, as far as precious metals, there's no country left in the world that still uses the gold standard. Every existing currency is fiat currency, which means it's worth something because the governments and people involved say it's worth something. It used to be (at least in the U.S.) that you could trot down to your nearest bank and convert all your dollars into the appropriate amount of gold. That was stopped in 1971, which is before many of the people here on E were born. For 38 years there's been only the word of the federal government to make the cash in your wallet valuable -- which does sound a little scary, but I still prefer that to the word of a counterfeiter, since I don't think they actually guarantee their work.
Plenty of people don't like fiat currency and think we should go back to the gold standard, but I don't know enough about economics to debate things like that. Like Oniya, I'm still having trouble with that graph. *scratches head*