I've recently gotten a 2012 MacBook Air 13". It is wonderful, however, I've been stressing about the life of the SSD. I understand that Apple probably would not sell an SSD machine with defaults that would ruin the SSD; however, I have some concerns.

Like all Mac laptops, by default it uses a hybrid sleep mode, so every time I close it, it writes up to 8 GB to the SSD. This is many, many times a day -- I'm in college, and I am always going to various places on campus, and the laptop almost always comes with me.

In addition, the default Time Machine configuration stores snapshots locally, and eventually, is allowed to fill 80% of the drive.

Both of these seem somewhat problematic to me -- sleeping and waking 10 times a day might write around 25% of the SSD capacity a day, and if I do let the mobile snapshots take up 80% of the drive, the static data on the drive will increase write amplification due to the SSD's wear leveling.

Am I worrying over nothing, or do I have a legitimate concern? If yes for the latter, what can I do to improve the life of the SSD?


1 Answer 1


Since OS X has TRIM support, the wear from writing 8 GB of sleepimage data would be spread out evenly across the drive by the controller in the SSD. Assuming 10,000 write cycles per cell and your estimate of 25% of drive capacity per day, you will be fine for 40,000 days (110 years) if you don't do anything else with the SSD.

That number could be completely wrong due to write amplification, but if the data is actually being written sequentially it shouldn't be a problem.

  • Thanks, this is something I should have thought of earlier. Also, it seems I was wrong about mobile Time Machine: Despite what Apple's documentation says, it only seems to keep a week's worth of backups, so there is much more free space on my drive than I suspected, which will help spread wear.
    – cablesm
    Jan 9, 2013 at 18:04

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