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I've been writing a script for my Mac Mini (2014) that does a speed test and logs the data to a database. All that works great, but the results were a lot lower than I was expecting.

I have a gigabit connection and my Mac Mini is hardwired directly to my Airport Extreme. I was expecting to see something around 900 Mbps, but it was more like 500 Mbps. I would usually blame my ISP at this point, but I decided to run the test from my Macbook Pro as well. My laptop was spitting out in the upper 900s consistently. My setup between my Mac Mini and my Macbook Pro are identical, both hardwired (with the same cable) to my Airport Extreme.

I looked up the specs for my Mac Mini and it says that it's 10/100/1000BASE-T https://support.apple.com/kb/sp710?locale=en_US

I'm confused, why am I getting such drastically different results?

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Mac minis ship with 5400 RPM spinning hard drives. Even if you’re using a Fusion Drive configuration, its solid state portion is likely taken up by more-frequently accessed files.

So assuming your downloaded data gets written to some temporary file, your benchmark is running off the mechanical drive. Add to that the overhead of recording logs to a separate database, which will further decrease your storage performance.

On the other hand, Apple laptops all ship with SSDs. An SSD should easily keep up with a Gbps connection.

The most probable scenario is your Mac mini is being bottlenecked by its hard drive.

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  • Ok so I realized that I have an iMac with gigabit ethernet and an SSD. I ran the speed test on there and it's showing slow speeds as well. I never thought a speed test could be so complicated. Any other thoughts?
    – wilkinnh
    Jun 30, 2017 at 12:34
  • Under System PreferencesNetworkEthernetAdvanced…Hardware, see if the Mac mini is configured for Full Duplex, which it should be. I wonder if there’s a limitation with the Mac mini’s PCIe lanes.
    – user11633
    Jun 30, 2017 at 13:57
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I've been suffering from this for a while now. I use my late 2014 mini regularly and replaced the ol' HDD with SSD which made it very well usable with 8G and Mojave. Enough to rule out I/O as a bottleneck.

I noticed it still gets around 350Mb/sec on speedtest.net (and derivatives) when my MBP can pull 850Mb/sec+ with the same tests.

What helped was to enable Jumbo Frames (from 1500 to 9000) in System Preferences → Network → Ethernet → Advanced… → Hardware. That immediately bumped it up from ~350Mb/sec to ~720Mb/sec.

Yes all my backbone supports jumbo frames.

So for me, SSD (for overall speed and usability) and Jumbo Frames (for network speeds) did the trick.

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