My 2012 MBA read and write speeds are a lot slower than expected. I know the figures are up to xyz but the machine is fast enough but to boot takes same time as my 2010 sata2 SSD MacBook. So please could you great folk here guide me thru reverting back to the old file system and high Sierra. I will make a TM and will migrate stuff back, there is not a lot as only 64GB SSD. I understand I will probably need format drive blank and start over which I'm fine with. I hope it will get some speed back. Write speed is almost half apples quoted speed and read down fair bit too.