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2018 MacBook Pro: SSD Speed vs Transfer Size
Related: 2015 MacBook Pro, 2017 iMac 5K, 2018 MacBook Pro, 4K and 5K display, iMac, iMac 5K, laptop, MacBook, MacBook Pro, Macs, SSD, Thunderbolt
MPG tested a fully-loaded Apple 2018 MacBook Pro 15-inch 2.9 GHz 32GB 2TB Radeon Pro 560X. The only better model is the same configuration with a 4TB SSD.
The SSD performance of the 2018 MacBook Pro (circles, solid lines) is outstanding for large transfers, but its weak point looks to be small reads. The emerging trend for SSDs from Apple has been less-good small I/O sizes in favor of higher speed for very large transfers.
The 2015 MacBook Pro (triangles, dotted lines) actually handily beats the 2018 MacBook Pro for reads from 32K through 512MB*—which are important speeds for overall performance.
* This might involve APFS, which in all of MPG’s testing has been shown to be inferior to macOS Extended for I/O speeds. The 2015 MacBook Pro was tested with macOS Extended after observing major performance losses from APFS with certain tasks (scanning folders, deleting files)—accordingly MPG reverted to macOS Extended on the 2015 MacBook Pro, which is/was a travel and work laptop whose compromise was unacceptable.
For 1MB and larger transfers, the 2018 MacBook Pro quickly leaves the 2015 MacBook Pro behind, and ditto for writes versus the 2017 iMac 5K.
These are real world figures through the OS X file system APIs, and thus reflect the performance available to applications.