No. Modern SSDs are quite sophisticated in how they handle wear leveling and are, for the most part, black boxes.

SSDs maintain a mapping of logical blocks (what your OS sees) to physical blocks (where the data is physically stored on the flash chips). For instance, when your computer writes to the logical block address 100, the SSD might map that to a physical block address of 200 (this is a very simplified). If you overwrite logical block address 100 again, the SSD might write to physical block address 300 and remap it, while not touching the data at physical block address 200. This let’s you avoid wearing out a particular part of the flash memory and instead spread the load out. It also means that someone could potentially rip the flash chips off the SSD, read them directly, and see data you thought was overwritten.

You can’t just overwrite the entire SSD either because most SSDs overprovision, e.g. physically have more storage than they report. This is for wear leveling and increased life span of the SSD. If you overwrite the entire SSD, there may be physical flash that was not being overwritten. You can try overwriting the drive multiple times, but because SSDs are black boxes, you can’t be 100% sure how it handles wear leveling and that all the data was actually overwritten.

• SLC -> Single-Level Cell, i.e. 1 bit per cell
• MLC -> Multi-Level Cell, i.e. 2 bits per cell
• TLC -> Triple-Level Cell, i.e. 3 bits per cell
• QLC -> Quad-Level Cell, i.e. 4 bits per cell

The more bits per cell you store, the more dense and therefore cheaper your flash chips can be for a give capacity. The downside is that it is slower and less reliable since you have to be able to write and read exponentially more voltage states per cell, e.g. 2 states for SLC, 4 states for MLC, 8 states for TLC, etc.

the timer has no idea if it was triggered during last boot. It only has the context of “this” boot, so it will do it right after a reboot and set a timer to start the service again after a week of uptime.

This is not correct. Persistent=true saves the last time the timer was run on disk. From the systemd.timer man page:

Takes a boolean argument. If true, the time when the service unit was last triggered is stored on disk. When the timer is activated, the service unit is triggered immediately if it would have been triggered at least once during the time when the timer was inactive.

OP needs to remove Requires=backup.service from the [Unit] section so it stops running it when it start the timer on boot.

You have the timer requiring backup.service, so it will run that service every time the timer starts on boot. Remove Requires=backup.service, and that will fix the issue.

USB 2 is 480 Mb/s, not 480 MB/s. 480 Mb/s is 60 MB/s, so the 500 MB/s from PCIe 2.0 x1 is quite a bit faster and is about the limit of what a SATA 3 interface could do. Also, sequential throughput isn’t nearly as important as most people think. Random IO, which NVMe drives excel at, will make a far more noticeable impact on real world performance.

I’ve been using PhotoPrism for the past couple of days and have really liked it.

I was considering Immich, but the rapid development cycle turned me off of it for now. I don’t want to have to deal with keeping up with patch notes and potential breaking changes. Immich also seems more focused on photo backups from your phone, which isn’t quite what I wanted. PhotoPrism just let me upload all my existing photos on the web ui.

I’d say give both a try. Both provide a docker-compose file, so you should be able to bring them up fairly quick.

I think the snapshot exists but is not mounted as a btrfs subvolume.

Is it not listed when you try running btrfs subvolume list .? You might need to change the . to a path that is on the array.

from the research I did, the @docker folder at the volume root holds all the volumes, images, subvolumes, etc. and I did copy that over.

Copying over the files wouldn’t be enough. You would actually need to create the subvolumes, e.g. btrfs subvolume create subvolume_name.

Do you happen to know if I find the snapshot folder and download it, will there be anything recoverable? Or would it just be like, hashes and unintelligble stuff?

Unfortunately, I am not familiar enough with how Synology does things, but a btrfs snapshot will just appear as normal directory with the files/directories in it. If Synology isn’t using btrfs for the snapshoting, I’m not sure what you’ll find.

I’ll preface this by saying I am not familiar with Synology, but I am using Docker and BTRFS (which I am assuming is being used on your Synology NAS).

Do you have SSH access or the ability to get a shell on the NAS? If you do, you can try running btrfs subvolume list . to see what subvolumes/snapshots are on your system. That will hopefully let you figure out where your data is. Once you narrow down where it is, you can try downloading it using an sftp client.

As an aside, the reason Docker threw a fit whenever you tried to update an image is that Docker was probably automatically using the BTRFS driver, which creates a new subvolume/snapshot for every image/layer. When you remove images, it would just remove all the subvolumes/snapshots. When you copied your files over, you probably didn’t remake the subvolumes. That would have caused issues when trying to remove images, or create new images/containers.

How are you passing the drives to the TrueNAS VM?

It’s your private key, but yes, you would need to keep it secret just like you would an SSH key.

The benefits of a VPN are that you don’t need to open ports up to the internet and rely on your individual services to be secure. Your VPN would authenticate users and ensure that the communication over the tunnel is encrypted (useful if you don’t want to set up SSL/https). They can also hide what services you are hosting or even hide the fact that you are even running a VPN.

Private keys are going to be far more secure than passwords since you really can’t brute force them in the same way you can passwords. Getting ahold of someone’s private key is probably going to be far more difficult than guessing their password. Even if an attacker were to get ahold of your private key, they would still need to contend with the security of your service, e.g. logging into it, which would be no worse than not having a VPN.