Hi, an overview 1st.

Been using my HTPC with Emby server and Emby Theatre for quite a few years now but have finally got fed up with having internal 3x 3.5 drives and 2 usb drive caddy's (a 2 bay Icy box and a 5 bay Terramaster) all a bit messy and built up and expanded over a number of years.

So i have decided to build a NAS for my movie and music collections and a place for my photos documents etc that i can then access from my various tablets (android) laptop, main PC's and wife's laptop.

I'm very used to building Windows PC's etc but not a Linux based NAS.

For the NAS software been looking at Unraid, hence my post here

So using parts left over from previous pc builds i have the following
Motherboard: Gigabyte A520I-AC Mini ITX
CPU: AMD Ryzen 4 4500G
Memory: 32gig Kingston DDR4
NVME to 6 port SATA converter (as the MB only has 4x SATA ports)
Power supply: Dagger Pro 850 watt SFX (new purchase)
Case: Jonsbo N1 New purchase (takes 5 x 3.5 drives and 2.5 SSD)
Hard Drives: 3x Toshiba 18TB enterprise NAS drives New purchase (what on earth has happened to hard drive and memory prices recently! lets hope the wife doesn't look at the bank statement his month)

Existing hard Drives all with movies and music on them
1 x 12TB HD
3 x 8TB HD's
2 x 6TB HD's
2 x 2TB HD's (to be retired)
1 x 16TB HD used as a back up (now full)

The plan is to install the 3x 18TB, the 16TB and the 12TB hard drives in the Jonsbo case along with a 512gig SSD (if the SSD is needed), have a 64gig Samsung USB flash drive as recommended in your installation guides of the Unraid software)
Have the 3x 8TB and the 2x 6TB drives in the Terramaster caddy as a JBOD set if possible

What i can't decide is how to configure the 3x 18TB, the 1x 16TB and the 1x 12TB

Raid configurations don't appear to let you use drives of different sizes or if they do then appears the total size is limited by the size of the smallest drive hence looking at Unraid as my software choice.
Have had a look at Snapraid and MergerFS as plugins but not sure if needed with Unraid as it appears to let you use the different size drives as a storage pool is that the correct terminology?

So looking for a bit of advice as to what to do.

Any help or suggestions gratefully received
Many thanks for reading
Keith W

Put all HDD in Unraid array, largest 2 drives as parity. One of the great features of Unraid is different sized disks protected by parity.

You will probably want to let Unraid format each array data disk as XFS. Unassigned Devices plugin will let you work with disks outside the array to transfer your data or transfer over the network if your existing storage is RAID.

A pool of 1 or more SSD as fast storage is useful for running dockers or caching.