I followed this video instruction https://youtu.be/eFHvIrdm9So to add a second, SSD harddisk (OWC brand) to a mid 2011 iMac.
After the installation is complete I rebooted the machine and tried to install using a usb thumbdrive with High Sierra installation image.
The usb thumbdrive is prepared by running the following command:
sudo /Applications/Install\ macOS\ High\ Sierra.app/Contents/Resources/createinstallmedia --volume /Volumes/MyThumbDrive
However after the reboot, the drive is not visible in the disk utility.
Reboot again and use the original harddisk. The SSD is still not visible.
How can I fix it?