I’m Hunter Perrin. I’m a software engineer.

I wrote an email service: https://port87.com

I write free software: https://github.com/sciactive

  • 3 Posts
  • 198 Comments
Joined 1 year ago
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Cake day: June 14th, 2023

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  • My setup is pretty safe. Every day it copies the root file system to its RAID. It copies them into folders named after the day of the week, so I always have 7 days of root fs backups. From there, I manually backup the RAID to a PC at my parents’ house every few days. This is started from the remote PC so that if any sort of malware infects my server, it can’t infect the backups.



  • Yeah, that could work if I could switch to zfs. I’m also using the built in backup feature on Crafty to do backups, and it just makes zip files in a directory. I like it because I can run commands inside the Minecraft server before the backup to tell anyone who’s on the server that a backup is happening, but I’m sure there’s a way to do that from a shell script too. It’s the need for putting in years worth of old backups that makes my use case need something very specific though.

    In the future I’m planning on making this work with S3 as the blob storage rather than the file system, so that’s something else that would make this stand out compared to FS based deduplication strategies (but that’s not built yet, so I can’t say that’s a differentiating feature yet). My ultimate goal is to have all my Minecraft backups deduplicated and stored in something like Backblaze, so I’m not taking up any space on my home server.


  • Btrfs does not have its own built in deduplication like zfs does. I’m surprised zfs has it turned on by default, considering file system level deduplication is fairly CPU and RAM intensive. But yeah, if you can use a deduplicated file system, go for it.

    In my use case, I’m not willing to move away from ext4 (on my home server, which is where this is running), and I don’t need all files on my file system to be deduplicated, just a set of files that I add to every day. I made this because it fits my use cases better than any other solution (this current use case, and some more I’m planning to implement in the future).

    As far as using snapshots to implement my current use case, it’s not possible. My Minecraft server runs on a different system than where I put my backups, and I want it that way. They are meant to be backups, not versions, and backups shouldn’t be stored on the same system. That server has also been migrated several times since I first started running it in 2019. I have back ups that go that far back too. So I need a system that I can put years worth of existing backups into, not just start taking backups now.


  • It very much is not. Again, btrfs will only deduplicate data under certain circumstances, like if you copy a file to a new location. If I take a USB stick with an 8gb movie file on it and copy that to btrfs twice, it will take up 16gb on disk. If I copy it to btrfs once, then copy it from there to a new location, it will take up 8gb on disk. Btrfs does not deduplicate files, it deduplicates copies. I want something that deduplicates files.

    If you run WebDAV on top of btrfs and try what I’m using it for, it literally will not deduplicate anything, because you’re always writing new files to it, not copying existing files.

    Triggering a snapshot with a cron job doesn’t mean it’s automatic to btrfs. The action still happens only when triggered. Btrfs doesn’t take snapshots for you.

    What good is management through SSH? I want a deduplicating file server, not a versioning file system I have to manage over SSH server. If I wanted versioning like that, I would just use git.

    And again, adding tools on top of btrfs to recreate something similar to what I’ve made here does not mean I reinvented btrfs. Btrfs is a COW FS. I wrote a deduplicating file server. I honestly can’t believe you don’t see the difference here. Like, are you trolling?

    I feel like you misinterpreted my post to mean that my use case is the only thing you could use my server for, and you’re just running with it, even though I’ve told you multiple times, I wrote a deduplicating file server, not an incremental backup system, and not a versioning system. The fact that I’m using it for incremental backups is inconsequential to what it actually does. It deduplicates files and serves them from WebDAV. AFAIK, there’s no other open source server that does that.


  • Having a separate tool do the work of making a snapshot doesn’t mean what I said is wrong. Snapshots are not automatic, with regard to btrfs. You can have a tool automatically make a snapshot, but btrfs won’t do it for you.

    My overall point is that a deduplicating file server has very little in common with btrfs snapshots. The original commenter looked at my use case for my own deduplicating file server and assumed that the server was the same thing as my use case.

    I think if they took the time to look at the server and see what it is actually doing, they would see that it is very different from btrfs.


  • Can you explain to me then:

    • How do you access the files in a previous snapshot without reverting to it?
    • How does btrfs automatically make its own snapshots?
    • How does btrfs serve the contents of previous snapshots across the network?
    • How can I copy the contents of all previous snapshots at once without imaging the partition?

    If you’re using other tools on top of btrfs to implement a deduplicating file server, then you can’t say I reinvented btrfs snapshots, can you?

    I don’t know how much clearer I can make the distinction between a copy on write file system and a deduplicating file server. They are completely different things for completely different purposes. The only thing they have in common is that they will deduplicate data, but a COW FS only deduplicates data under certain conditions. My server will deduplicate every file across its entire file store.

    I get that people on Lemmy love to shit on other people’s accomplishments. I’ve never posted anything on here without it being criticized, but saying I “reinvented btrfs snapshots” is quite possibly the worst, most inaccurate take anyone has ever had on any of my posts.


  • So, to be clear, this is not a versioning system. I’m just kind of using it for that with my Minecraft backups. This is a deduplicating file server. It takes the files you give it and deduplicates them. Then, later, you can pull them out again. I am using it for backups, but it is also not a backup system.

    I think I made it seem in my post like what I’m using it for is what it should be used for, or the only thing it can be used for. My use case is just one of many that you can use a deduplicating file server for.




  • Not at all. Btrfs snapshots:

    • aren’t accessible unless you revert to them
    • only happen when you manually trigger them
    • don’t deduplicate files in the file system, just across snapshots
    • are handled at the file-system level (meaning you’d have to create a separate file system, or at least a separate subvolume if you’re already using btrfs, to make them with an exclusive set of files)
    • don’t have access controls beyond Linux’ basic file controls (so sharing a server will be complicated)
    • aren’t served across the network (you can serve a btrfs file system, but then you can’t access a previous snapshot)
    • aren’t portable (you can’t just copy a set of files to a new server, you have to image the partition)

    They serve a very different purpose than a deduplicating file server. Now, there are other deduplicating file servers, but I don’t know of any that are open source and run on Linux.