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Help! Why is my new SSD running SO SLOW?

This is the first time I’m posting a question on the internet regarding these type of issues, so please bear with me. I have a MacBook Pro 13” late 2011, and I read that I could upgrade the HDD to an SSD to make it run much faster. My brother got me the NAND SSD 860 EVO SATA 6Gb/s (500GB) to do the swap. I formatted it to MacOS Extended Journaled and cloned my HDD to it.

Now, before doing the actual physical swap of the HDD for the SSD, I wanted to check its speed, so I used BlackMagic Speed test to do so. My original HDD showed results around 70Mb/s on writing and 98Mb/s on reading. However, when I tested the speed of the SSD it shows no more than 28MB/s on both writing and reading! (I’m using a SATA Hard drive/SSD to USB 3.0 Adapter to connect it to my laptop).

I’ve tried formatting the drive to APFS (because they told me it was the best option since my Mac is running High Sierra), and also thought it might be the USB port I was using on my laptop, so I changed it to the other one, but nothing changed :(

I know the SSD would probably work much faster if it was already installed internally in the laptop, but I just find it hard to believe that the difference between speeds would be so much (This SSD is supposed to do sequential reads of up to 550Mb/S and writes up to 520Mb/s)

Please, I’m really new with trying to do these type of things on my own, and I’m not sure what I’m doing wrong. I’m SO lost and don’t really know what to do. Any kind of guidance would be very much appreciated.

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Hey Ana! I think Dan may have misunderstood the situation. Take a look at my answer below and let me know if this explains things for you!

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Ana del Cid,

I understand the confusion.

The main reason you’re seeing those speeds is because your MBP doesn’t have USB 3.0 ports, only USB 2.0 ports. This means that even though you’re using an adapter that’s equipped with USB 3.0, it’s limited by the transfer speed of the laptops port. In computers, we say that “your transfer speed is only as fast as the slowest link.”

To better illustrate:

SSD (6Gbps) —> USB 3.0 Adapter (5 Gbps) —> USB 2.0 Port (480 Mbps)

The fastest speed you can get is 480 Mbps, or 60 MB/s (Mbps is Megabits, MB/s is Megabytes), which explains your 28 MB/s

As a benchmark for comparison:

  • USB 2.0 = 480 Mbps or 60 MB/s
  • USB 3.0 = 5 Gbps or 640 MB/s
  • MacBook Internal Storage Bus Speed = 6 Gbps or 750 MB/s

In simple terms, when installing your SSD internally, your read/writes should see at least an 18x increase in speed, which will also be at least 5x faster than your HDD now. Pretty big difference if you ask me!

If this helps you, let me know by upvoting my answer!

Have an awesome night,

- Alex

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Alex... THANK YOU SO MUCH! I'm really a newbie in all of this and I was freaking out a bit. Again, thank you so much, I really appreciate you taking the time to explain all of these basic things to me. It's all so clear now DUH LOL! You're an angel! Thanx again :)!

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@anabdelcid - The I/O of a given connection has its own limits and different versions often times have improved speed USB2 > USB3.0 > USB3.1 (USB-C). You also can't always compare across I/O standards either. Yes, all very confusing! And it's getting worse.

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OK lets clarify the whole HFS+ Vs APFS issue. IF you had a PCIe/NVMe SSD then going to APFS makes sense! But thats not what you have. I don’t recommend using APFS on SATA based drives as the queue depth is so shallow you loose performance unlike PCIe/NVMe.

Getting back to your problem:

You have either an older version of the HD SATA cable or its bad. You’ll need MacBook Pro 13" Unibody (Mid 2012) Hard Drive Cable and yes this is a 2012 version of the cable. Follow this guide MacBook Pro 13" Unibody Late 2011 Hard Drive Cable Replacement. In addition you want to place a strip of electricians tape on the uppercase where the cable crosses over and you don’t want the crease the cable! Sharp bends damage it. You want smooth arcs around the bends & corners.

Once you’ve got the cable replaced I strongly recommend you erase & reformat the drive, and stick with Sierra!

How to create a bootable macOS Sierra installer drive

MacBook Pro 13" Unibody (Mid 2012) Hard Drive Cable图片

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MacBook Pro 13" Unibody (Mid 2012) Hard Drive Cable

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Hey Dan, great advice. Though, I think you may have misunderstood the situation. Ana was saying she hadn't yet installed the SSD and was just testing the read/writes from an external USB 3.0 adapter and comparing them to the speeds of her internal HDD, which explains the slow SSD speeds. Take a look at my answer below. Ana probably did not know of the slower USB 2.0 bus speeds.

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Otherwise, great insight on HFS+ vs. APFS! @danj

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Thank you for answering Dan. I think I may have made the whole question kinda confusing but, luckily Alex was able to see all through it lol. Thank you very much though :)!

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@alexrobinson - Sorry I missed the USB issue your question was on the long side so I jumped to the more common issue this series has. I should have gone to bed ;-) 11:30PM

@alexrobinson - This is so common a problem with both the HFS+ & APFS file systems and the old/worn HD SATA cable.

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@danj Ah makes sense. Well at still learned something from you, I can admit that!

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