I need to copy files from 1 hard drive to another.

Try using Disk Utility/Restore to copy the files to a new location. Please note that this will reformat the destination partition.

How to create a boot clone

HD or SSD. I suspect HD.

You can try running Disk Utility to run Disk First/Repair Disk.

Disk Utility for Mac: Repair a disk using Disk Utility

You can try re-formating the drive anew—loosing all data.

http://www.howtogeek.com/236978/how-to-repair-disk-and-file-system-problems-on-y our-mac/

Try different cable connections, different ports.

You can consider the possibility the drive is failing.

Scott Crawford3 wrote:

I bought a new, faster hard drive (800 Mbps vs 400 Mbps), and I need to copy files from the old hard drive to my new one. I tried dragged them from old to new and got a ton of aliases that won’t work after the old hard drive is turned off and disconnected.

I can't recall what triggers this behaviour but basically you need to mash buttons until the Finder does as you expect 🙂

e.g.

Hold command when dragging & Finder will 'move' the file to another disk

Hold alt when dragging & Finder will 'duplicate' the file to another disk

Hold alt+command when dragging & Finder will 'alias' the file to another disk

The icon on the cursor indicates what will happen.

Finder is a terrible tool to make large copies of data for several reasons…

1. It does not resume when a copy fails
2. It does not verify a copy was successful
3. It can often fail for vague reasons simply giving you an error code
4. Permission are just one reason for failing to copy - Finder is vague about giving you full access to everything

If you want exact copies do not not use Finder. Use a third party tool like Carbon Copy Cloner, SuperDuper! Another option is apps like Chronosync that can clone specific folders & verify data has copied correctly.

http://bombich.com/

http://bombich.com/

http://econtechnologies.com/

If you must do it for free then you can use Disk Utility to clone one disk onto another via the 'restore' feature. Or use Terminal commands.

As for the disk speed - how is the disk connected? Are you sure the OS is not the slowest link in the chain? If the OS is running slow then it can make the disk appear to be the issue. Eject the disk, power it down & confirm your Mac is actually performing OK without the disk. Spinning disks will also perform slower the more data you put on them…

https://macperformanceguide.com/Storage-WhyYouNeedMoreThanYouNeed.html

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