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I recently purchased Carbon Copy Cloner, and set it up to backup my Mac to an external SSD (Crucial X6, not especially high-performance). This works wonders, and I can finish an incremental backup in ~1 minute.

I would also like to backup to a makeshift NAS (a Raspberry Pi 4 running Samba, with a mechanical hard drive connected to it). Unfortunately the performance of this setup is unacceptable: any kind of backup, even if essentially nothing was changed, takes many hours (say ~8 hours). This is so long that I'll often have to pack up the laptop to take it to work before the backup is finished.

Clearly the main issue is with small files; on CCC's progress graph I see that the rate of processing files is in the order of a few tens of files per second. Looking at CPU usage in the Raspberry Pi, it is always close to 100% -- which is very odd for processing tens of files per second at a transfer rate of << 1 MB/s. For the initial backup, I mounted this hard drive in a faster PC and got improved performance, but not too much, say 2 or 3 times faster. Using the PC, rather than the Raspberry Pi, as the NAS is not an option, and nevertheless it is still too slow.

Networking speed is not the issue: I can easily get upwards of 50 MB/s when copying large files. The Pi is connected by gigabit Ethernet, and the Mac by WiFi 6E, right next to the router -- it can and does achieve faster-than-gigabit transfer speeds in other contexts.

It seems like this an issue with Samba. I'm thinking there must be some sort of configuration I can change, either on the server (Raspberry Pi 4) or the client (Mac) to achieve a considerable speedup and reduction in CPU usage. How can I improve Samba performance through client- or server-side configurations to achieve improved performance?

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  • What exactly is the question here?
    – nohillside
    Dec 6, 2023 at 9:43
  • How to improve Samba performance (e.g. through client-or server-side configurations), or more generally, other alternatives to get fast backups to NAS.
    – swineone
    Dec 6, 2023 at 10:01
  • Might help to put this at the top of the post, it kind of gets lost in the post.
    – nohillside
    Dec 6, 2023 at 10:38
  • Also, did you try rsync to have something to compare the CCC results to?
    – nohillside
    Dec 6, 2023 at 10:39
  • Thanks for the idea, I will add it to the list of experiments to perform.
    – swineone
    Dec 6, 2023 at 10:42

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Since posting the question, I've become convinced that SMB performance is hopeless for this task. I've investigated other alternatives and eventually settled on Borg and its Vorta GUI. After the initial backup (which took < 2 hours), daily incremental backups are finishing in a couple of minutes at most.

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