First Nas Build Need infomation about securing data

Hello i’m starting a project i’m building a nas server this will be my first ever nas but im just confused about raids. After doing a bit of research if a drive fails and you have a extra drive in your nas your data is safe. But i also seen online if 2 drives fail and you have one extra drive your toast data lost?

Just need infomation how raids work and the best way to secure data if hard drives fails

This Nas project is not complete yet i still got to buy few parts till im up and running

CPU: intel i5 7600k
Ram: Corsair 32GB DDR4
Hard Drive: Not Bought Yet (Planning on x2 4TB OR 6TB hard drives not sure what brand to pick)
Boot Drive 256gb PNY SSD
PSU: Not Bought yet

With Truenas you can choose different types of storage configurations:

  • Stripe: One or more drives put togheter. If ANY drives fails, ALL data is gone.
  • Mirror: 2 or more drives that are basically copies of each other. 2-way mirror, you can lose 1 drive, 3-way mirror, you can lose 2 drives, etc…
  • RAIDZ1: Uses parity to reconstruct data that was on 1 lost drive, meaning you can lose 1 drive
  • RAIDZ2: Uses parity to reconstruct data that was on 2 lost drives, meaning you can lose 2 drives
  • RAIDZ3: Uses parity to reconstruct data that was on 3 lost drives, meaning you can lose 3 drives.

With 2 drives, you could do either a 2 drives stripe (DONT DO IT), or a 2-way mirror (go for that).

Thanks for the info that all makes sense

i would be willing to buy a extra Drive to do Raidz1 as that secures my data or is a 2-way mirror just safe as doing Raidz1

In both cases you can lose only 1 drive.