Hey
@marcelovvm,
What kind of disc are you using?
It would be important to get proper NAS drives, like the Seagate IronWolf I am using. Western Digital have their "Red" branch of disks that are presented as NAS drives also. Here, the thing that is important is to be sure not to get yourself some SMR drives. Western Digital sold some of their Red drives as NAS drive without saying at first that they were SMRs. They reacted to that but you still must be extra careful here to avoid them.
The reason it is important is that so many drives produce a lot of heat and vibration. Also, they must spin all the time (to spin down and up drives all day long will kill them in no time). Regular and cheap hard drives are rarely designed to sustain such hard conditions. There is also the firmware that is different. A desktop drive will fight its storage all day long to recover some data when a sector is hard to read. It does so because should it fails, that data will be lost. In a NAS, that means the NAS server will have to wait forever when bad sectors happen. A NAS drive is meant to be used in a structure with redundancy. Should a specific sector be hard to read, the drive will not wait too long and will return an error. The NAS will then use the redundancy to recover the data from somewhere else and then work to fix the bad sector or mark is as such without lost.
Also, it would be good for you to plan how much space you need, by how much will that increase over time and what security margin are you comfortable with. That will give you an idea of the usable space you need. Because you said it is for hosting Proxmox hosts, it means that you need a maximum of IOPS. For that, you do not have much choice and must go with mirrors. That will be 8 mirrors of 2 drives each.
Next step will be to plan your backups. No single server, FreeNAS or other, can be more than a single point of failure. So how will you do your backups ? Do you need another server ? More storage ? ... Also, should you go for the lowest side on your hard drive, a failure will be more probable. That is, the backups will be of even higher importance.
Have fun designing your setup,
