everything I learned about SSD upgrades (OWC Aura, MBA 11")

[belm0]

Background: I upgraded my MacBookAir6,1 to a MacBookAir7,1 (both core i7) with an undersized SSD. Since I read something reputable that said the SSD's were incompatible (turned out not to be true), I went about evaluating 3rd party drives (OWC Aura N and Aura Pro X2). I'm very battery-life conscious; also wanted an SSD with a native connector.

Here is the TLDR of what I learned on this journey. Most of this info I just couldn't find anywhere and had to discover it myself.

• MBA 11" has slower SSD bus than 13" and other Mac laptops. It will max out at ~700 MB/s read/write for 2 channels (e.g. Aura N), 1400 MB/s for 4 channels (Aura Pro X2), regardless of the drive spec.
• stock 512GB AHCI drive on MacBookAir6,1 (SM0512F) actually had reasonable performance: ~650 MB/s read/write
• stock 128GB drive on MacBookAir7,1 (AP0128H) is NVMe, 4 channel, and seems to be tuned for power savings by limiting write performance (or it's due to small size?): 990 MB/s read, 320 MB/s write. Its idle power usage is extremely low (more below).
• Aura Pro X2 (512GB tested) has huge idle power draw (despite receiving good power usage marks from AnandTech review). Literally it drains the battery of my idle MacBookAir7,1 over 50% faster than either of my stock drives. For perspective, the difference was larger than max vs. min screen brightness. It's important that the OS & firmware know how to manage the storage low power modes.
• MacBookAir7,1 (Broadwell) has significantly lower power use than MacBookAir6,1 (50% when idle?)
• you can clone bootable drives just fine with Disk Utility, no need for 3rd party software. Just be sure to use Disk Utility from Catalina or newer.
• you can get reasonable estimates of total system power usage by using "pmset -g rawlog", which logs current being drawn from the battery every minute. By running this with different devices (e.g. SSD) you can discover their relative power draw.
• NVMe drives are fully functional (fast startup to boot screen and correctly resume from disk hibernate) as long as the computer firmware is from Catalina or better. With High Sierra firmware I'd see a long delay to boot screen (even after NVRAM reset), and resume from disk hibernate fails.

Following details idle power use measurements for various device combinations. Unfortunately I returned my Aura N before discovering how to use "pmset", and that drive is supposed to have a fraction of the Pro X2 power use due to the 2 channel controller (it literally had 3 chips on the PCB, single side). I ended up returning the Pro X2 as well once I confirmed its effect on battery life, and am content with my stock AHCI drive despite the modest max speeds. If the drive fails I'd probably go back for the Aura N.

Please do your own measurements, as I may have made measurement errors or incorrect assumptions.

power draw of idle system (min display brightness, wifi off)
​

config	size MB	pmset mA *	conditions
MacBookAir6,1 - AP0128H	128	490	Catalina
MacBookAir6,1 - Aura Pro X2	512	600	Catalina
MacBookAir7,1 - AP0128H	128	220	Catalina
MacBookAir7,1 - Aura Pro X2	512	630	Catalina
MacBookAir7,1 - Aura Pro X2	512	670	High Sierra, not quite idle
MacBookAir7,1 - SM0512F	512	230	High Sierra, not quite idle

* for reference, the pmset delta between min and max display brightness is ~310 mA

 

[Audit13]

Check out the excellent thread here: https://forums.macrumors.com/thread....2034976/page-314?post=29333863#post-29333863