external ssd as boot and data disk iMac 2015 Big Sur

Thank you for the help. I tried following the steps. it took about 18 hours for the CCC.

I’m not sure what I did wrong as after the CCC finished the external ssd does not show up in the system settings startup disk screen but does show in disk utilities.

i guess i’m try again

I tried the CCC (ver 6) twice. When I look at disk utility, it shows the SSD with two parts / volumes under the main SSD drive name (it end in media). One is HD and the other HD – Data.

But it doesn’t show as a boot disk in disk startup.

it looks like CCC copied everything from the internal try to the external SSD, but its not showing as a boot disk.

I read somewhere problems with Catalina and maybe reading CCC copies.

Big Sur is the latest OS for my mid 2015 iMac.

Not sure what else to try.

I tried that, as it was mentioned, but I only see the internal HD.

taking a step back of how I got here.

What I was trying to do is have an external SSD as a boot and data on the same external SSD. I wanted to avoid using the internal hard drive still connected to the inside of my iMac because the speed on my computer is so slow.

but am I thinking about this correctly?

Maybe I only need to make the external SSD drive a boot or a data instead of both?

The goal in purchasing the external SSD drive was to speed up my computer. quite often It is quite slow when doing just normal tasks. Internet browser use; grading multiple assignments with open tabs on multiple web browsers. No video editing involved here.