I returned this unit and bought ts-473a instead. I didn’t opened it so i can’t tell for sure. People say that the soldered ones were released during COVID and most probably those new units have the normal slots.

Hello, Prices can indeed fluctuate on a daily basis. That's why we provide a price evolution tool on each item page. Note that by adding an item to a wish list, you will automatically be notified by e-mail of any price reductions. For more information, click on the following link: https://www.digitec.ch/fr/wiki/6028

My device claimed that the 8GB was not expandable. After receiving it, however, I realised that there was a free slot. So I ordered an additional 8GB module and installed it. Now I have 16GB without any problems. 8GB is rather tight.

A QNAP NAS with 4 drive bays can basically hold a maximum of 6 x 22 TB disks or even larger ones if firmware is required. If you set up the system with RAID5, this would result in a capacity of 5 x 22 TB, i.e. around 110 TB gross. Net, of course, it is less, probably just under 100 TB. But since a 22 TB disk costs almost 600 Swiss francs, this is not really a good idea. It would be better to buy a NAS with 8 drive bays, then you can also use a lot of storage, but you don't have to buy expensive disks. My recommendation would be this one, it doesn't cost much more and you could also create a RAID5 with 8 x 16 TB, which also makes 112 TB of gross storage available. The bottom line is that the 8 drive NAS is not much more expensive, but you save a lot of money on the disks (16 TB costs about 400 vs about 600 for 22 TB): QNAP TS-832PX-4G (0 TB)

I have mounted my TS-664 with 6x 18 TB and created a RAID 10 static volume with 48 TB. According to QNAP, the max. volume size is 250 TB.