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2021 MacBook Pro M1 Max: SSD Speed vs Transfer Size

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MPG tested the Apple 16.2" MacBook Pro with M1 Max Chip Z14X000HR, a maxed-out model in all ways except 4TB SSD instead of the maximum 8TB SSD.

2021 MacBook Pro M1 Max


Real world speeds through the file system using diglloydTools DiskTester.
disktester run-sequential-suite
--test-size 8G

This test charts the real-world speed for various transfer sizes for both reads and writes, because small I/O sizes are much slower than larger ones.

For example, 32K transfers are highly inefficient vs 1MB transfers—there is a difference of 32X times as many operating system calls to transfer 1MB in 32K chunks as with one call to transfer a 1MB chunk.

Fast small transfers translate to a more responsive system overall, while fast large transfers translate to better throughput for applications processing very large files, or very large numbers of moderate and large files.

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Transfer speed vs transfer size

disktester run-sequential-suite --test-size 8G

The 2021 MacBook Pro M1 Max shows stunningly fast write speeds. Fast enough that one wonders if there is something sketchy going on (eg caching). Because there is no way it is honestly writing 32K chunks at 7.1GB/sec. Moreover the drive has read speeds little better than the 2020 iMac 5K until reads get into the 4MiB size. Apple is doing something new and unusual for writes, hopefully not a data-loss risk thing.

See the next test for more weird stuff.

Flash Drive (SSD) Speed vs Transfer Size from 32K through 512MB, APFS
2021 MacBook Pro M1 Max vs 2019 iMac 5K, 2020 iMac 5K

Sustained Performance Filling Capacity

disktester fill-volume

Test volume size, APFS: 3TB ~= 2.78 TiB.

Write behavior is unlike anything MPG has ever seen in an Apple internal SSD. The behavior is repeatable.

To see an abrupt breakdown in SSD write speed for sustained writes suggests a 2-tier flash drive. The plummet occurs at file 479 of 1000, equating to 1331 GiB = 1430GB, or about 35% of the 4TB flash drive. Which makes no sense for a 2-tier design (1/3 fast flash, 2/3 slower).

Turning to thermal throttling as a theory, why the sudden plummet? With thermal throttling, one would expect a steady degradation, not an abrupt change.

Even the degraded write speed is in line with prior internal Mac SSDs (3.2 to 3.3 GB/sec) on iMac 5K, Mac Pro, etc. But when not degraded, the 7GB/sec figure is pretty awesome.

Further research is needed. Based on invoking the test a 2nd time, it appears that the SSD speed “regenerates” after the first test, so long as there is some time in-between. TBD.

The results for reads here are in excellent agreement with the test above: a bit over 5GB/sec, which is far above the ~3.3GB/sec achievable in prior Macs.

As reader Don H puts it:

Of course almost no one would have a task that requires this magnitude of data transfer in the real world, and even then the performance is still quite good, even with a slowdown. Short of the PCI-based storage in your Mac Pro this appears to be the fastest storage in any Mac to date. (It’s odd that the early write performance exceeds the read performance by so much, however.)

2.78GiB = 2.985GB per file.

Sustained transfer speed writing 1000 files of 2.78GiB each to 3TB ~= 2.78TiB APFS volume
2021 MacBook Pro M1 Max
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