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I have a Retina MacBook Pro Mid-2014 with a 256GB drive, which is small for my needs so I need to use an external Hard Drive.

I'm using a WD 4TB My Passport where I store a lot of pictures and videos, I have my Photos.app library in the external drive and it is kind of slow. So I'm thinking about buying an external SSD to have a better experience working with my files. I think I would probably get a SanDisk 2TB Extreme Portable External SSD but if I can find a better similarly priced drive I could go for that one.

Considering my computer has USB 3.0, Would this be an improvement in speed?

From what I've understood it would be about a 3x speed improvement but I'm not sure and I don't want to buy a more expensive drive that does the same thing that the one I already have.

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    I do recommend getting a good non-external SSD, and putting it in an enclosure yourself. that way you can make sure you get a top quality drive. Generally speaking, pre-built externals use the cheapest disks that the company has to offer. SSD will be able to use much more of your available bandwidth than a mechanical disk will, so you should see an improvement, though it would be better if you could mount it internally, so the best advice I could give is upgrade your internal disk. partition it if you want the new capacity to be a different volume.
    – Frank Thomas
    Commented Jun 23, 2020 at 3:21
  • I would NOT recommend DYI enclosures, at least you need to pay serious attention to cooling design of it. WD BLACK P50 is a good SSD with high throughput and finessed interface, the best at the moment.amazon.com/WD_Black-500GB-Portable-External-Compatible/dp/… At USB3.0 rates you can get 440-460 MBps on streaming loads.
    – Ale..chenski
    Commented Jun 23, 2020 at 6:02

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It should be an improvement in speed. USB 3.0 has a throughput of 5 Gb/s. Typical HDD's have a read speed of around 160 MB/s, which doesn't fully utilize USB 3.0's throughput. On the other hand, typical SATA-based SSD's have typical read speeds of 500 MB/s (which approaches but does not surpass USB 3.0's throughput). So, for most uses, you should see a speed increase.

There are NVMe SSD drives, for example, which offer much faster read/write speeds compared to older SATA-based drives (think thousands of MB/s). Such drives would be bottlenecked if used through externally USB 3.0. This shouldn't be a concern for you in this scenario, since the drive you listed doesn't fully occupy USB 3.0's speeds. Even if it did, you'll notice a speed increase since HDD's operate much slower than USB 3.0's speeds.

(For other readers considering using an NVMe drive externally, consider using a thunderbolt-based enclosure, such as this. There are also standalone external SSDs that use thunderbolt and offer faster speeds than what USB 3.0 would allow)

More importantly, SSD's excel at random read accesses. For example, if you try copying many small files from an HDD, you'll notice that read speed tanks (e.g., down to hundreds of KB or less) even though the HDD is technically capable of much faster transmission. This is because HDD's need seeking time to move their heads between accessing each file. Thus, the above read speeds are sustained speeds, where the device is reading data from one location. SSD's need negligible time between each file access, so you should expect pretty fast speeds even if your accessing many files at once. This distinction is very apparent when open a folder that contains a large number of files (similar to refreshing to your media library in your Photos app).

I did notice that your WD drive lists faster "maximum" read speeds than the SanDisk SSD. I suspect that you'd probably won't notice these speeds (either because it's wrong or because it only occurs in rare circumstances). You can try benchmarking your current drive to see if it is capable of those speeds. Most benchmarking software will also give you different results for sustained and random accesses. Again, note that your WD drive will only achieve those speeds when transferring single, large files.

The summary of this all is: yes, you should expect faster speeds if you buy the SSD you listed. The SATA-based SSD should be faster while not fully utilizing USB 3.0's maximum speeds. The SSD will also benefit you if your working with many different "small" files (like photos).

You'll notice less of a benefit if you are only storing big files (maybe your videos, depending on how large they are). If you are waiting a long time to refresh your library, an SSD will definitely help there (since this task requires accessing many different files).

Further reading:

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  • Somebody down voted your answer but I don't see why, maybe they should have left a comment. You answer seems adequate... thanks.
    – loco.loop
    Commented Jun 23, 2020 at 2:28
  • @loco.loop It might be downvoted because it has inaccurate statements. SSD do have different interfaces, and different internal flash organization. some are SATA (600 MB/s), some are NVMe (up to 2000 -2400 MBps and above).
    – Ale..chenski
    Commented Jun 23, 2020 at 6:12
  • @Ale..chenski I've addressed your comment in my post. For the purposes of your scenario, OP, you won't need to worry about NVMe speeds since the drive you listed doesn't fully populate USB 3.0's speeds. You'll also notice a speed increase when switching to a "SATA-like" external SSD, since there are still heaps faster than traditional HDDs.
    – emilh
    Commented Jun 23, 2020 at 14:34
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    For other readers, please note that while downvotes are a great tool, I can't always improve my answer to them unless someone tells me what is wrong with it first. For those with enough rep, you can also edit my answer.
    – emilh
    Commented Jun 23, 2020 at 14:35
  • I kind of go ahead and disagree with you wrt NVMe media in USB enclosures. Every interface has protocol/link overhead. If you have SATA-like SSD, where the raw data rate is very close to USB 3.0 (Gen1), two overheads will kind of sum up, which will encroach into overall device throughput. But if you have a 2000MB/s NVMe device behind a USB bridge, the NVMe overhead will be out of equations, and you will get maximum possible performance over USB 3.0 link. It might be 10% or something, but anyway...
    – Ale..chenski
    Commented Jun 23, 2020 at 20:17
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I realize this post is two years old, but I have valuable information to add. (This thread is one of the top results when anyone googles HDD versus SSD USB3 speed, so it might prove helpful to some people, even though it’s old.)

I have a MacBook Pro similar to the OP. Using Blackmagic Disk Speed Test, the difference between an HDD and an SSD using USB 3.0 is dramatic. I found an SSD to be roughly 7 times faster than an HDD. The HDD speed was in the 60-70MB/s range. The SSD was over 400MB/s. The test was repeated using different enclosures and different drives, but produced consistent results.

So now we know for sure, using a real-world test.

I also noted that the SSD runs about 8% faster in a UASP enclosure compared to an older non-UASP one. (That’s a different of around 30MB/s)

Your mileage may vary, of course. My opinions are guaranteed to be valid, or your money back.

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There is a lot of talk about Maximum throughput HDD vs SDD and USB being limited by 5gbps. The largest gain by far for SSD over HDD is random access times - HDDs are in 10ms range while SSDs are instantaneous. So yes SDD WILL BE MUCH BETTER for normal OS usage. If you're looking for storage only HDD is fine.

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According to the theory, speed should be increased since usb 3.0 has upto 5gbps of writing speed and NVMe ssd drives have upto 3.7GBps - 5GBps. Even the non-NVMe ssd drives hav 300 - 500MBps of sequential transferring speed. Since that, using an external ssd drive will improve and bring the best output from the USB3.0 , But the thing is the purpose of the ssd drives. They are designed to run OS And Software to improve the performance of computers. Performance will be increased according to the data transferring speed between Ram and Storage devices. Also since they're very expensive, i would recommend to use hdd as portable hard and use ssds for only internal use to get the best out of your resources.

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  • "They are designed to run OS And Software" - that was true for early SSDs, those times have passed
    – Máté Juhász
    Commented Jun 23, 2020 at 5:19
  • It's also not quite clear what is meant by being "designed to run OS and Software". Also, why should SSDs be used internally only? I like them as external drives since they aren't as susceptible to physical shocks like HDDs are (I learned this the hard way).
    – emilh
    Commented Jun 23, 2020 at 14:39
  • SSDs originally offered too little space to be useful for storing bulk data such as movies, music or photos. Larger SSDs were prohibitively expensive except for some professional users for whom the performance improvements were worth the extra cost. In those days it was common to use an SSD for OS and software, and a separate large HDD for data. These days, you can get a 1-2 TB top-quality SSD for 100-200 USD/EUR. At these prices, SSDs are replacing HDDs in many use case scenarios, including as external drives.I still have a 2 TB HDD for backups and a 8 TB RAID10 in my NAS. SSD everywhere else
    – Gene Pavlovsky
    Commented Feb 6, 2023 at 16:01

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