Luckily, there are many things you can try before fixing the external hard drive or external disks issue. If this external drive isn’t showing up on Mac system, some deeper issues might need to be fixed. Why you must fix it immediately: Data on your Mac is stored on a hard drive, whether it’s internal or external. What you might not know: There can be many reasons for an external hard drive not reading a Mac - poor connection, faulty cable, dirty USB, or, in the worst-case scenario, corrupt hard drive data. But sometimes you meet the 'external hard drive not showing us' issue.

Each bay may have its own external interface, or the drives may be routed through a RAID controller and presented to the Mac using a single interface.What you know: When you plug in an external drive disk utility into your Mac, you expect it to pop up and be showing up on mac in Locations in Finder - next to your remote disk and the computer itself. The external interfaces available include USB 2, USB 3, FireWire, eSATA (and other SATA types), and Thunderbolt. They usually hold 3.5-inch drives, but many also support SSDs. Multi-bay enclosures range from holding two drives to holding 16 or more drives. Multi-bay enclosures: This type of enclosure uses multiple bays or docks.This type of enclosure usually has its own power supply. External interfaces include USB 2, USB 3, FireWire, eSATA, and Thunderbolt. In some cases, two SSDs can be installed in this enclosure size.

3.5-inch external enclosures: Used with the standard hard drives and SSDs found in most desktop computers.

The enclosures can be bus-powered or have their own power supplies. Common interface options include USB 2, USB 3, and eSATA. Performance depends mostly on the type of external interface used to connect the enclosure to the Mac.

2.5-inch external enclosures: Designed for use with the types of hard drives and SSDs commonly installed in laptop computers.

This type of enclosure should perform as well as any other external device that uses the same type of computer interface. Power is usually supplied by the interface bus (USB or FireWire), but some enclosures use external power supplies (wall warts).

1.8-inch external enclosures: Designed to hold a single 1.8-inch hard drive or SSD.

The downside is their slowness, especially when you're writing data to them.

USB flash drives: Small, portable, and relatively inexpensive, these house capacities ranging from 2 GB to 2 TB.

External hard drives for macbook air