USB 3.0 and USB 3.1 Gen 1 connections have a theoretical bandwidth of 5Gbps or 640MBps, and typically provide 300MBps to 400MBps of throughput, while USB 3.1 Gen 2 can manage twice that. SATA II interfaces can handle up to 3Gbps ( gigabits per second) or 375MBps ( megabytes per second), while SATA III can manage 6Gbps or 750MBps.Īfter that, there are external hard drives that use either USB (Universal Serial Bus) or Thunderbolt connections. There are fast flash memory cards that slot directly into the computer’s main board, and internal SSDs and hard drives that use Serial ATA connections. There are lots of options between these two extremes. These storage systems are very cheap, very slow, and a very long way from the CPU. At the other extreme, data that is rarely needed can be stored on tapes or Blu-ray discs that may take minutes or even hours to retrieve. In general, fast, expensive storage lives as close to the processor as possible, with the ultimate being cache memory that is actually on the CPU. Photograph: andrewsafonov/Getty Images/iStockphotoĬomputer storage has always been hierarchical, and today it covers a wide range of speeds and prices.

The storage hierarchyĮxternal drives are the answer for adding more storage on the cheap to most laptops, but also desktops that are difficult to upgrade. You will be comparing your fast new Mac Mini with your slow old one, and this will probably have a much bigger impact than the differences between internal and external SSDs. However, you should see a dramatic improvement whichever type of storage you choose. Suffice it to say that the best way to tell what kind of external SSD and connection you really need – which could be a version of USB 3.0 rather than Thunderbolt – is to test it with your own software and data. That will make far more difference to performance than picking a drive that looks “fast” because it’s good at sequential reads. However, if you need to do a lot of reads and writes, it’s better to choose an SSD that does those things quickly. You don’t need a fast external drive if you mainly use it for streaming music and videos. For example, SSDs can stream data much faster than they can read and write random data. Inside the PC, they include the path to the processor and how many lanes (see below) are available for data. If speed is critical – which I doubt – then a 2TB internal drive will be faster than a 128GB or 250GB internal drive in the same class.Īn external SSD’s real-world performance will also depend on many other factors, including the type of storage and the interface chips used. However, you should be aware that big SSDs are faster than small SSDs, because the controller can write to more modules at the same time. The specific question is impossible to answer because there are so many variables.

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