It's actually hard to say. You might be very lucky, someone else might be very unlucky. Generally, RAID was 'invented' to operate on cheap, commodity hardware,

It's actually hard to say. You might be very lucky, someone else might be very unlucky. Generally, RAID was 'invented' to operate on cheap, commodity hardware, where the failure rate might be high. When it comes to data, most reliable one you can find (mostly due to its probe size and lack of competitive reports of similar size) are Backblaze's drives reliability reports.