Checking the speed of Hard Disk(s) ?

I want to install Mojave on an external hard disk.

But I have to choose one - from those I have - that is fast (not the slower one).

So I am searching a free speed testing application for HD.

Do you know and use some ? TIA.

I use HELIOS LanTest for local and remote HD testing.

blackmagic disk speed test

You can use my LAN Speed Test app (made with Xojo). The free Lite version will do what you need.

Aja System Test Lite on the App Store is another good Speed tool.