Apple advertises the new MacBook Air as being instant on as a result of the internal SSD. That’s mostly untrue. From a completely powered off state the MacBook Air still takes time to boot. That time is significantly reduced compared to the old MacBook Air and any other Mac with a conventional hard drive. It’s even a shorter boot than my MacBook Pro with a SandForce SF-1200 based SSD in it:
| System Performance Comparison | ||||||
| Boot | Shut Down | Sleep | Awake | |||
| 11-inch MacBook Air | 15.5 seconds | 2.2 seconds | 1.0 second | 1.63 seconds | ||
| 13-inch MacBook Air | 14.4 seconds | 1.9 seconds | 1.0 second | 1.56 seconds | ||
| 13-inch MacBook Air (Late 2008) | 34.4 seconds | 2.9 seconds | 1.6 seconds | 4.19 seconds | ||
| 15-inch MacBook Pro (SF-1200 SSD) | 19.1 seconds | 1.8 seconds | 1.5 seconds | 2.3 seconds | ||
| 15-inch MacBook Pro (Mid 2009, HDD) | 34.2 seconds | 2.8 seconds | 1.8 seconds | 2.1 seconds | ||
You'll notice that even the SF-1200 SSD in my 15-inch MacBook Pro takes longer to boot than these new Airs. Apple does customize the firmware on its SSDs. I’d be willing to bet the SSD in the MacBook Air has tight integration with OS X to guarantee quicker than normal boot times.
Clearly the new Air isn't instant on from a boot standpoint, but it's pretty much there from a recover-from-sleep standpoint. The new Airs both go to sleep and wake up from sleep quicker than any of the other Macs, including my upgraded 15-inch Core i7 MacBook Pro. Again, nothing can trump Apple's tight integration between hardware and software.
Apple likes to work with two different controller manufacturers for SSDs: Samsung and Toshiba. iFixit already confirmed Toshiba is in the new MacBook Air with its teardown:
The 11-inch MacBook Air SSD, courtesy of iFixit
The SSD isn’t in an industry standard form factor, although the connector appears to be either micro or mini SATA. Presumably 3rd party SSD manufacturers (ahem, SandForce partners I’m looking at you) could produce drop in replacements for the MacBook Air SSD.
There’s nothing particularly innovative about the form factor of the SSD, other than Apple did away with the unnecessary space a 2.5” SSD would require. Just as SSDs will break the traditional SATA interface barriers, we’ll see the same happen to form factors as well.
The part number on the Toshiba controller may look familiar to some of you. It’s the same controller that’s in Kingston’s SSDNow V+ Series and the SSDNow V Series Boot Drive. I reviewed the latter not too long ago and found that it was a good drive for the money, and here’s the kicker: the SSDNow V Series Boot Drive was amazingly resilient when written to without TRIM support. Its performance hardly dropped as a result of normal desktop use. This is very important because although OS X 10.6.4 has a field for reporting TRIM support on an SSD, the instruction isn’t actually supported by the OS. Even the new MacBook Airs don’t ship with a version of OS X with TRIM support.
The SSD only has four NAND devices on it. Typically that would mean some very low transfer speeds, particularly on writes. But each one of those four devices has at least 16GB of NAND, spread across multiple planes and die. With the right firmware, you should be able to extract a good deal of parallelism from this architecture. Apple and Toshiba apparently do just that.
While most value SSDs top out at under 100MB/s, we get nearly 200MB/s sequential reads and writes out of the SSD in the new MacBook Air. And fortunately, Apple hasn’t only focused on sequential performance. The random read/write performance of the new MacBook Air SSD isn’t terrible:
Random write performance is of course the weak point, but you’ll notice that it’s actually higher than the Kingston drive that uses the same controller. While Apple would’ve been better off striking a deal with Intel or SandForce for the controller in the MacBook Air, the Toshiba controller isn’t horrible.
As I mentioned earlier, resilience is very important as OS X still doesn’t support TRIM. I filled the drive with garbage and then tortured it for 20 minutes with random writes. The resulting performance drop was noticeable, but not unbearable:
A single pass of sequential writes restores performance to normal:
This tells us two things. First, through normal use the drive should be able to recover its performance over time (assuming you give it enough spare area). And second, if there’s any idle garbage collection in Apple’s custom firmware for the Toshiba controller it should be able to keep the drive running at peak performance even without TRIM supported in the OS. I don’t have a good way of measuring whether or not there’s GC enabled on the drive in OS X, but I suspect Apple is (at least it appears to be doing so on the Mac Pro’s SSDs).
Overall I’m pleased with Apple’s SSD selection. It could’ve been a lot better but it could’ve been a lot worse. The MacBook Airs in their default configuration have better IO performance than any other standard config Mac sold on the market today, including the Mac Pro.
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