My Mini PC fried my SSD 🙁
A cautionary tale for you, I've experienced two separate instances of my Dell Ultra Small Form Factor (USFF) PCs frying my SSDs. These two Dell Optiplex 9020M were being used as Proxmox nodes each using a 2.5" SATA SSD as the boot drive, with a 512 GB M2 SATA SSD for storage. I'm sharing my experience due to the prevalence of this type of Mini PC/USFF device on eBay which are frequently purchased for home lab use.
Background
Each node was purchased and deployed at a different time although each of them had their 2.5" SSD fail after approximately 8 months and my suspicion is that they were slow cooked over a long period of time.
The disks were not the best brands - the cheapest option on Amazon at the time I was commissioning the units - therefore the quality of the drives was not the best in the market, however, before moving to Proxmox the mini PCs were a single disk setup running Ubuntu for Docker containers and they lasted well over a year with a similar brand SSD. I had also used the same brand and model of drives in another server and they have lasted for over 2 years in a Micro ATX form factor case. All of this does point the finger at the thermals.
Failure theory
Micro PCs like these obviously have limited internal space for expansion and they don't have the best cooling systems although I would have expected the cooling to be sufficient to cool devices it had slots for.
My theory on the failure is that while the temperature in the mini PCs was within the operating temperature range of the 2.5" SSDs, the temperature was in the upper part of the range resulting in a 'slow cook' process over time. As noted, the SSDs I used were not the best brands and may be less tolerant due to the quality.
The M2 SSD was likely emitting heat which was being concentrated on the 2.5" SSD which is positioned directly above it.
I should point out that the PCs were installed on a shelf in my AV rack which has ample airflow and doesn't get hot. They were physically separated, not stacked or positioned close together.
One of the mini PCs was used for Proxmox Backup Server which was an always on node but only had to do any work once a day to back up a small home lab. The services being backed up don't change very much between jobs meaning that each backup window was basically dealing with small incremental changes, the typical total backup time was less than 10 minutes.
Knowing that the same 2.5" SSD drives perform well in larger form factor systems with better cooling gives me confidence in my theory being true. The reality is that most of the devices found on eBay would have been used in offices and would only have a single drive installed, the diversity of slots likely for flexibility rather than maximising the storage amount.
Conclusion
The combination of the USFF mini PC with two disks is something I am now avoiding as I don't want the risk of the same thing happening, whether that be with a cheap SSD from Amazon or risking purchasing a more expensive brand and having that die on me. My Proxmox nodes are now Small Form Factor (SFF) as a minimum.
The temptation to use USFF devices is great as there are just so many out there for good prices and often will find them being shipped with SSD included. The SSDs included will almost definitely be the same flavour of cheap Amazon brand, possibly used. If you plan to only use a single disk it should be fine, but adding that second drive could be a problem.