The MacBook Air: Thoroughly Reviewedby Anand Lal Shimpi on February 13, 2008 12:00 AM EST
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MacBook Air Performance: SSD vs. Mechanical HDD
We took the same MacBook Air and just swapped drives for running these tests, you can't get more scientific methody than that. First up are some synthetic tests to help set expectations, for that we turned to XBench 1.3.
XBench isn't a particularly good benchmark for OS X, but it does have a basic drive performance test that suits our needs:
|XBench 1.3 256KB block Disk Tests||80GB 4200RPM HDD||64GB SSD|
|Sequential - Uncached Writes||28.4MB/s||24.6MB/s|
|Sequential - Uncached Reads||28.0MB/s||49.9MB/s|
|Random - Uncached Writes||20.6MB/s||17.8MB/s|
|Random - Uncached Reads||13.0MB/s||49.2MB/s|
The trends are pretty clear here: write speed is about 17% faster on the mechanical HDD while read speeds are much higher on the SSD, particularly when they aren't sequential reads. Since the mechanical drive has to worry about locating data on a spinning platter, random data spread out over the relatively slow spinning platter takes time to access. The SSD benefits from having an equal access latency to data regardless of where it's located in the drive's flash memory.
While most desktop applications are quite sequential in nature, multitasking can change I/O access patterns considerably.
Our first set of real world tests on the SSD are basic stopwatch application launch tests. We took 7 applications and timed how long they take to start up on the mechanical drive vs. the SSD:
|Application Launch Time Tests||80GB 4200RPM HDD||64GB SSD|
|Adobe Photoshop CS3||18.0s||6.9s|
|iWork '08 - Pages||11.0s||3.5s|
|iWork '08 - Keynote||13.0s||6.3s|
|iWork '08 - Numbers||7.1s||3.5s|
|Microsoft Word 2008||28.8s||11.0s|
|System Boot Time||54.4s||32.5s|
The SSD completely destroys the mechanical disk in application launch times, and these results aren't just numerical, they are very noticeable in using the system. The SSD is noticeably faster in application launches, accessing files in Finder and spotlight searches. After I used the SSD MacBook Air, I tossed the standard HDD back in and honestly thought something was wrong - it felt significantly slower, despite feeling mostly "fine" before I was exposed to the SSD.
Most application level benchmarks however favor the higher write speeds of the mechanical disk instead:
|Application Benchmarks||80GB 4200RPM HDD||64GB SSD|
|Word 2008 - Compare Docs||107.8s||109.3s|
|PowerPoint 2008 + Word, Print PDF||149.0s||162.6s|
|Quicktime H.264 Encode||5.6m||5.8m|
Most of these benchmarks show the SSD as slightly slower than the standard HDD, but a couple are noticeably faster on the standard drive thanks to its write speed advantage. The SSD recommendation would be an easier one if the benchmarks clearly leaned in one direction or another, but it's not as difficult as you might think on first glance.
The split between reads and writes on a desktop system is biased towards read performance, so you're more likely to notice the SSD's faster read speeds than its slower write speeds. The theory was echoed in my real world usage of the machine, the SSD was just faster.