A better organized and streamlined file system.You may have an issue with your system using a dual drive config. Apple macOS High Sierra most important features are: Intelligent Tracking Prevention to remove advertisements in Safari by using machine learning. It also brings a lot of powerful new system technologies that will help users reimagine the way they interact with their Mac.

Secure VPN client for Big Sur, Catalina, Mojave, and High Sierra. Review this: OWC Data Doubler locate your exact model and if it has a red note you'll need a different drive in the bay.Get a fast, secure, easy-to-use VPN app for macOS. This is a MacBook issue not the carrier or the drives.

As SW pointed out a common issue with the 13' models is the HD SATA cable breaks down so it interferes with the movement of the data, you'll need to replace it.TeamViewer for macOS Establish incoming and outgoing connections between devices Real-time remote access and support Collaborate online, participate in.Here's the IFIXIT guide: MacBook Pro 13' Unibody Mid 2012 Hard Drive Cable Replacement and here's the part you'll need: MacBook Pro 13' Unibody (Mid 2012) Hard Drive Cable. The latter two components are optional and can be ommitted when choosing 'custom install', they are only needed. Contains R 4.1.1 framework, R.app GUI 1.77 in 64-bit for Intel Macs, Tcl/Tk 8.6.6 X11 libraries and Texinfo 6.7. R 4.1.1 binary for macOS 10.13 ( High Sierra) and higher, Intel 64-bit build, signed and notarized package.

If you want to compatibility with older systems you'll need to install Sierra instead then you'll have the older GUID/Journaled File System (HPFS)Well, I can start off I can save you a few bucks by getting this version of the cable IF163-041-2 as you don't need to get the one with the bracket, saving you 5 bucks!As to why you are paying more here, IFIXIT is also a movement as such you've also helping push efforts to support repair & reuse globally! Here's more on that: IFIXIT.ORGIn its self, they also offer a better warranty on the part than the fly by night posts you see on Amazon & eBay.As to part numbers, Apple constantly improves their parts. As you're installing High Sierra you only have one choice GUID/APFS. Also don't over do the bends as the fold wires inside are fragile.I would redo your SSD's drives format and re-install the OS again, then restore your files from your backup.

New Mac Os Sierra