I'm going to be in the market fairly soon for some expanded storage. I run Plex Server on my main desktop, but other than Plex, uTorrent, and casual web browsing, I really don't use this computer for anything else. Nevertheless, because I built it a decade ago or more, I beefed it up about 6 months ago with a used mobo/CPU/RAM combo I found on eBay (i7-3770 3.4 GHz), and it now runs Plex beautifully. I have 4 internal drives in it -- two mirrored 500 GB drives with the OS (Win7 Pro) and other data (torrent downloads, etc.), and two mirrored 8 TB drives that hold all of the media. I'm down to about 750 GB on these drives and need to think about how to best expand it. I *may* be able to sneak another pair of drives inside, but I need to check the mobo and power supply. Even if those would handle two more drives, it would be a cable routing mess, and I'd worry about airflow.
I'm pondering going the NAS route, but the majority of the advice I find online about Plex and NAS is for people looking to RUN their server on the NAS. I don't see any reason for me to do that since I'm happy with my desktop playing that role. Additionally, my understanding is that the most powerful NAS devices are limited in their transcoding ability compared to a decent desktop CPU. So unless someone talks me out of it, I'm literally looking for the most economical NAS without any consideration of its suitability for transcoding video. I simply need it to hold the media.
As for storage capacity, at this point I'd like to add another 12 TB, so my first thought was to simply buy and shuck two 12-TB Easystores and mirror them just like my current 8-TB drives are mirrored. I'm open to other RAID configurations to maximize storage space while retaining redundancy -- I have no experience with anything other than RAID 0 and 1. Is the DS418 overkill for my purpose? Obviously I wouldn't use all 4 bays immediately, but I'd like to future-proof a bit by having the option to add drives later.
Essentially, I'm looking for the most economical and reliable option for adding storage and redundancy. Cloud backups aren't an option -- my upload speed is capped at 20 mbps and monthly data cap is 2 TB.