Question How many bays and HD should I get if I buy a Synology NAS?

[modeonoff]

Hi, I have decided to buy a Synology NAS. At first I planned to buy a 4-bay one. However, I don't know how much disk space and drives I will end up in 5 years. Not sure if I should get a 5 or 6-bay NAS instead of a 4-bay NAS which could allow expansion of more drives via eSATA.
Currently, I have to backup the following:

1. Work PC with a 2TB main disk. Used about 1.25TB already.
2. iPad with a 256GB storage (generates about 256GB of photos and videos every 10 months or so)
3. Time machine backup of a Mac I already sold (about 1TB SSD)
4. iPhone 128GB
5. Linux development system 1TB
6. Old drives (Windows, Max, Linux) made over the past 20 years. Maybe about 1TB in total. Not decided if I should copy the data to the NAS or just leave them in the drawers.

Given the above usage, is a 4-bay NAS sufficient? How much storage/drive do you recommend if I just buy one or two drives initially?

If I buy a 4-bay NAS with one 4TB drive initially. Is it easy to add higher capacity drives later and change the RAID configuration?
Is it a bad idea to mix drives of different sizes? For example, one 4TB, two to three 6 or 8TB HDD later?

Note that one reason I don't get one 8 or 10TB HDD at the beginning is that besides the cost, the higher the capacity, the noisier it is. Is this really true?

 

[USAFRet]

Thanks for the analysis. So just treat the NAS as one type of storage that could also lose data like other types of storage, rather than some kind of magical box that can prevent data lost even 1-2 drive(s) fail.

Exactly.
Always have a 2nd/3rd level of backup.

RAID 5 can only survive loss of one physical drive, not two.
RAID 1 loses a lot of otherwise available space. 4x 4TB + RAID 1 = 4TB drive space.


As said, in the vast majority of consumer use, RAID of any type is not needed at all.