Will RAID 1 keep my files safe in case of bad sectors?

If a bad sector suddenly develops and a file is written to it, no. The file may be corrupted. Also, bad sectors are usually detected on read operations. However, if bad sector(s) are detected, RAID 1 will (likely) fail the disk. A disk doesn't have to completely die to be failed by RAID.

If you're looking for bad sector protection, you might want to look at BTRFS or ZFS file systems. These file systems put check sum values on files, where a file will be rewritten if an error is detected. It's referred to, by some, as "bitrot" protection.

Zitat von BBmine

Thanks! I asked because the other day a hard drive inside a laptop got some bad sectors and that made me think about what RAID would do.

(When bad sectors start appearing, it's time to get your data off of the drive. Complete failure in the future is likely and it may be imminent.)

Just some quick notes on RAID:
RAID is NOT BACKUP. While it may protect you from a hard drive failure, there are many scenarios where you could lose the array. Good backup is a must and it doesn't have to be expensive.

RAID 0 - The insane array. This one is designed solely for faster throughput, and makes no sense in a NAS role. If either of the two hard drives fail, it's over. Everything is lost. (If you're after performance for a Desktop PC, you'd be far better off with a single SSD.)
RAID 1 - A mirrored disk set. The advantage is, if one disk fails, the other still has your data. The cost is one complete HD. (2 drives, at 4TB each = a 4TB array)
RAID 5 - A stripped volume. The advantage is, if one disk fails, the other disks still have your data. (A minimum of 3 disks is required and there is no maximum limit, in theory.) There's a read and write performance increase. The cost is, 1 drive to store parity. (3 drives, at 4TB each = an 8TB array)

Unless you're buying a server case and motherboard, the above covers most scenarios you may be considering.

Zitat von BBmine

I'm not sure if I'm buying a server case, but I think I'm going to buy a regular motherboard.

If you have a place to put it, there are a number of large inexpensive cases available that will warehouse a lot of hard drives. I have a "server" motherboard but, in the essentials, all it has over most regular MOBO's is ECC ram and a RAID utility.

If you're really interested in RAID, you'll be hooking up more drives than average and it makes sense to keep your boot drive out of the array. So, when you shop,I believe you'd want to note the number of sata drive connections your new MOBO has to offer. Running RAID 1 is easy at only two sata ports. To run RAID5, even if you boot from a USB drive (which is what I'm doing), you'll need a minimum of 3 sata connections. I'd argue 4 sata connections is minimum for RAID5, because it allows for a standy spare. (That would be 5, if booting from a standard hard drive or SSD.)

If you're you're looking for file parity protection, you almost might think about "Snapraid". OMV has a plugin for it. Snapriad requires a bit more hands on than standard RAID but it does give more flexability. Info on Snapraid, how it works and what it's for, can be found here. -> Snapraid