Member Avatar for mcwoof

Hey all,

I just bought an iomega external USB drive, Ive hooked it up to my mac but it's not recognising the drive.

It's formatted in FAT32; is that not mac compatible?

It's a 1TB drive, do I need to partition it into smaller sections?

Which format should I use given that I'll be using it with windows and mac computers?

It's confusing stuff!!

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  • Latest Post Latest Post by mjdodd

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Short answer: macOS can read and write FAT32, but FAT32 is a poor choice for a modern 1 TB drive shared between Mac and Windows. FAT32 limits a single file to ~4 GB and Windows’ built‑in formatter will refuse to create FAT32 volumes larger than 32 GB. There’s no need to split a 1 TB disk purely to “make it work” — a better approach is to pick a filesystem designed for large volumes.

For cross‑platform use pick exFAT (good support on modern macOS and Windows, large file/support for big volumes). Typical format workflow:

  • On macOS: open Disk Utility, select the physical device (not just a volume), Erase -> Format: exFAT -> Scheme: GUID Partition Map -> Erase. Use diskutil list in Terminal to confirm the device if Disk Utility doesn’t show it.
  • On Windows: open Disk Management, initialize the disk (choose GPT for 1 TB if prompted), create a new volume and format it as exFAT. Back up first — erasing destroys all data.

Troubleshooting when the Mac “doesn’t recognise” the disk (as reported): try a different USB cable/port (avoid unpowered hubs), check System Information / System Report -> USB to see if the enclosure is enumerated, run Disk Utility First Aid if the device appears but won’t mount, and uninstall any bundled Iomega utilities if present (as noted those can cause problems). If files appear to copy but then vanish (like described) it’s often write‑caching/unclean eject or failing hardware — always properly eject before unplugging; if data is critical stop writing to the disk and run recovery tools or consult a recovery service.

If platform features are needed: use APFS/HFS+ for Mac‑only, NTFS for Windows‑only (macOS can read NTFS but cannot write without third‑party drivers such as Paragon/Tuxera). exFAT is the simplest modern compromise for mixed environments.

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Member Avatar for mjdodd

I think you have to use fat as macs use that! However fat does have a problem that there is a limit on the size of files that can be saved in FAT. I have also had a lot of trouble with the Iomega software that came with the external hard disk and eventually got rid of that software (and then reformatted) and now it works well but I do not have a mac so I went down the NTFS route.
There maybe some Mac software that lets it read NTFS.
M

Member Avatar for Andrew44

(right-click) My Computer > Manage > Disk Management > (right-click) the external drive and select "Format" > Choose whether you want a "Quick Format" or "Enable File and Folder Compression".

Member Avatar for GreyWill

There is a problem with my USB that whenever i copy some data into it ,first of all it shows right then after removing and again connecting it shows it empty .Is there any solution for this ?

commented: Random dribble and spam links -4
Member Avatar for mjdodd

I think that to solve your problem do a google search under FAT partition size FAT has a 'wall' of maximum partition size of 4 Gb. You will have to split the Terrabyte into more partitions if you are going to use FAT. (which is MAC & windows compatible). Thus you will end up with the same space but spread over other 'logical' drives.
As far as the USB not being recognised it maybe worth shutting down explorer and restarting it ( or even refresh) as some USB drives do not always reconnect via explorer!

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