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MacBook Air Solid State Drive (SSD) Performance

Further below is how the 251GB MacBook Air solid state drive (SSD) performs over 95% of its capacity (an 11GB system was installed).

Apple is not truthful about the SSD capacity; it formats to less than 250.66GB, yet is advertised as a 256GB drive
Actual capacity is not 256GB!

Apple is not truthful about the SSD capacity; it formats to less than 250.66GB, yet is advertised as a 256GB drive.

Most likely the missing 5+ gigabytes are used for some internal housekeeping. But if that were the case, then OWC could call their 400GB drive a 512GB, their 200GB a 256GB, etc.

I consider this false and misleading advertising, even if the difference is only 2%.

The first thing I did was to wipe out the Apple system install, and install a minimal one, which totalled about 9.22GB.

Performance on the Apple SSD is outstanding compared to hard drives, which at their best would top out at about 100MB/sec and then steadily decline (read Why You Need More Space Than You Need). But the performance is below that of top-grade SSDs, like the OWC Mercury Extreme Pro.

Note the regular downward spikes in performance due to some kind of internal housekeeping. This is with a brand-new drive; of some concern is how well it holds up over time. See my Severe Duty Test of the Apple 512GB SSD.

The 251GB SSD in the MacBook Air appears to perform a bit less well than the 512GB (500GB) SSD offered for the Mac Pro. But both drives show the same pattern of regular downward spikes, including a nasty glitch at about the half-way mark. How well this SSD will hold up over time remains to be seen. I won’t be toasting mine in any severe duty test.

Performance of the Apple 256GB (251GB) SSD in the Apple MacBook Air
Performance of the Apple 256GB (251GB) SSD in the Apple MacBook Air

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