MacBook Air 2010 SSD Performance
Graphed below is how the 251GB MacBook Air solid state drive (SSD) performs over 95% of its capacity (an 11GB system was installed).
Update Jan 28, 2011: see an alternative to the Apple SSD.
The MacBook Air SSD formats to 250.66GB, yet is advertised as a 256GB drive. This is false advertising, even if the difference is only 2%. Apple should be truthful. Apple lies about the 512GB SSD for the Mac Pro also (12GB gone missing).
With the new Apple iMath (imaginary number i?), OWC could call their Mercury Extreme Pro RE 400GB drive a 512GB, their 200GB a 256GB, etc, since that’s how much actual flash memory is on those SSDs.
Most likely the missing 5+ gigabytes on the Apple 256GB SSD are used for some internal housekeeping. If that’s what the design requires, so be it, but advertising as if it were usable space is wrong. No one would accept this for gasoline or cookie dough or Cheerios.
Testing the SSD
The first thing I did was to wipe out the Apple system install with its extra bloatware, and install a minimal one, which totalled about 9.22GB prior to upgrades and a few apps.
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 250.66GB 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.