i had hardrive failures me in the past so i want to minimize the risk of losing large amount of data i cant store online in cloud
RAID will not guarantee against file loss in all cases. Only multiple backups in different places will protect you against most eventualities.
https://www.raidisnotabackup.com/
The minimum you should be aiming at is 3 copies of all important files on different disk drives, in 3 different locations. You can use hard disks, SSDs, USB memory sticks, optical disks, tapes (or even the dreaded cloud which I only use for file transfers). It doesn't matter where you store files, provided they're not all in one machine.
As I said earlier, if your computer gets hit by Ransomware, both copies of files in a RAID1 array could be encrypted. If you don't have any offline copies physically disconnected from your machine at the time of a virus attack, you'll have lost all your data. RAID won't protect it.
Similarly, if you make a mistake and delete a large folder full of files and don't spot the error before they're overwritten with new data, both copies on a RAID1 array will be lost. As with Ransomware, if you don't have another copy elsewhere, RAID won't protect you.
In the rare event of a catastrophic ATX PSU failure and the dying PSU zaps all the drives with high voltage, your hard disks will stop working. If the hard drives have gone up in smoke, RAID will not protect you.
The simple fact is RAID is not a good backup strategy. It merely reduces the chances of data loss in some circumstances when a drive fails.
As I mentioned earlier, both 1TB drives in my RAID1 array slowly developed faults and I was none the wiser for a long time. This was many years ago and I learned my lesson. Don't trust your only copy of important files to a single RAID system.
For many people with modest storage requirements, 3 separate (non RAID) drives in 3 different locations are enough to safeguard data. You should never have all three copies connected to one machine at the same time, in case of Ransomware or PSU failure. All 3 copies could get zapped.
would raid 1 be safer? the more drives you have the more you can lose?? not sure about the rebuilding speed
RAID1 is safer than RAID0, which provides no protection against disk failure, just extra speed.
Rebuilding (resilvering) speed depends on the amount of data and can take hours or days.
Other versions of RAID would provide more protection than RAID1.
In RAID5, you can lose one drive from the array and (in theory) you should not lose any data.
In RAID6, you can lose any two drives from the array and (in theory) your data will still be safe.
There are other versions of RAID if you care to investigate.
I run four RAID-Z2 arrays (equivalent to RAID6) in an Operating System called TrueNAS Core.
https://www.truenas.com/truenas-core/
Three of the arrays are made up from 8 drives per array. The fourth array contains only 6 drives.
All 8 (or 6) drives are exactly the same capacity, e.g. 8 x 6TB drives, 6 x 4TB drives.
In RAID-Z2 (RAID6) you automatically lose two drives' capacity due to parity, hence 8 x 6TB provides only 6 x 6TB (36TB) of storage space. 6 x 4TB provides only 4 x 4TB = 16TB of storage space. You sacrifice total drive space for security in RAID5 or RAID6.
The more drives you use in an array, the greater the risk of drive failure. For bigger arrays (over 10 drives) I'd switch to RAID-Z3, which allows for up to 3 drives to fail, or split the array into two VDEVs.
I keep multiple copies of important data on the four RAID-Z2 systems. I keep more backups on individual hard disks in desktop computers. I even backup data to 800GB tapes, then click the write-protect tab to prevent accidental or malicious deletion. Yes it's total overkill and I'm paranoid, but I'm more likely to preserve my data than you are with a single RAID array.
If you want to check for "bit rot" and file errors, you can run Data Scrub tasks and SMART Tests on a regular basis. These helps to uncover file and disk degradation.
sure i have a good reason. but its kind of my own buseniss if i want it or not
Sure it's your business, not mine, as to why you want to run RAID, but I hope you can see that it's not a "magic bandaid" that protects against file loss. That's what backups are for. At the moment you're just trusting to luck, with all your eggs in one RAID basket. I just hope it doesn't end in disaster.
