自己看吧。2012Mid的MBA跟新固件，更新不了的，换新盘。
http://www.apple.com/cn/support/macbookair-flashdrive/
Apple has determined that certain 64GB and 128GB flash storage drives used in the previous generation of MacBook Air systems may fail. These systems were sold between June 2012 through June 2013.
Apple or an Apple Authorized Service Provider (AASP) will replace affected flash storage drives, free of charge.
If you ran a firmware update and were directed to this web page, skip to Replacement Process section for next steps.
To see if your drive may be affected, go to the Mac App Store, click on Updates and choose the MacBook Air Flash Storage Firmware Update 1.1. The firmware update will test your drive to see if it is affected. You will be directed back to this page for next steps if needed.
IMPORTANT: If your drive is affected, we strongly recommend that you do not install any operating system updates or new applications. We also recommend backing up your data on a regular basis until you receive a replacement drive. Learn more about backup options
Replacement Process If your MacBook Air has an affected flash drive, please contact one of the Apple service providers below to schedule an appointment to get your drive replaced:
Apple Retail Store - Set up an appointment with a Genius. Apple Authorized Service Provider - Find one here. Apple Technical Support - Contact us for local service options. Before you bring your MacBook Air in for service, please back up your data. Learn more about backup options.
Additional Information You will be able to reinstall the operating system version that shipped with your product by going to the Mac App Store. Any other applications or other data should be restored from the back up that you made before the replacement.
If you believe you have paid for a repair or replacement due to this issue, contact Apple regarding a refund.
This worldwide Apple program does not extend the standard warranty coverage of the MacBook Air.
The program covers affected MacBook Air for three years after the first retail sale of the unit. Apple will continue to evaluate service data and will provide further updates to this program as needed.