Optimal RAID for NAS?

Question

Backup

Good for all!
The office has several databases and virtual machines that need to be protected from loss. The total amount of data is 4.5 TB. For backup I plan to use NAS - Thecus N7700 Pro. Performing a backup daily. The backup will grow, but not much, by 10 GB per week maximum.
Question: what is the best way to build a disk array in a NAS? Current options:
A) 2 HDDs of 6 TB each in a RAID1 mirror
B) 6 HDDs of 2 TB each in RAID6 (5 for raid and one for hot backup)
Option A seems to be better, cheaper, and simpler. Yes, only the reliability of RAID1 worries - after all, if one disk fails, then for the second such a probability becomes very likely. So right? In the meantime, I'll be copying terabytes to a new disk... Then the second disk will hiccup. Need the opinion of an experienced Jedi.
Or maybe there are better options? The requirements are simple: it is necessary that in case of problems there is a guaranteed backup, write-read speeds are not critical.

Answer 1

Why option "B"?
Option "A" is completely optimal for you.
Moreover, disks do not work like that: set it and forget it (the disk is dead, crying).
NAS's are able to warn if something is wrong with the disk. And even more so, the disks are not made of cotton, if you take new disks (not used), then they will quietly serve you for many, many years.
For NAS, I personally recommend Western Digital RED. This is a special series of discs released by Western Digital for data storage. These drives are extremely fault tolerant. They can work 24/7, as the manufacturer claims, the operating time until the end of fault tolerance is 1,000,000 hours! (If I'm not mistaken) with 24/7. So do not worry, and even if the drive starts to fail, the NAS will warn about it, and you can save your files without even the slightest loss.
All the best. ;)

Answer 2

Optimal RAID for NAS?

Depends on tasks.
In the case of a destroyed first raid, you will copy data from the mirror disk - in fact, a linear load on the disk, the data will be copied quickly and without straining the disk. In the case of a destroyed fifth raid, you will copy data and checksums from two disks, the load mode is random in small blocks. In general, copying will take a long time, and create a huge load on the disk. Accordingly, the probability of failure of this drive increases.

The requirements are simple: it is necessary that in case of problems there is a guaranteed backup, write-read speeds are not critical.

NAS with disks without raid, even better two NAS.

Answer 3

The presence of RAID does not eliminate the need for a full backup to a separate place (highly desirable!!!!!!!)
Otherwise, you will catch a virus, a ransomware, or a raid controller will die .... and stay with live disks without information ...

Answer 4

after all, if one disk fails, then for the second such a probability becomes very likely.

You have a strange understanding of probabilities.
Event #1: Disk 1 failed.
Event #2: Disk 2 failed.
Event #3: Drives 1 and 2 have failed.
Event #1 does not increase the probability of event #2 by itself. Just when it has come, the chance that event #3 will come (which depends on two events at once and is the product of their probabilities) is higher. However, one must understand that the fact that one disk has failed the second disk will not start to work worse. Unless if both disks are from a defective batch, but then both of them already work poorly initially. And this is a rather unlikely event.
In short: RAID1 is the simplest and REALLY reliable solution for you.