Backup Taking Too Long

• Where is tour catalog stored?
• Where is your backup stored?
• In LrC is any sync to the cloud running?
• Is this a new problem (id it behave before?)

I am backing up my lightroom catalog and it's been 15 hours so far. Is that normal for a catalog with 170,000+ images on lightroom?...

By @kathryn_greenwood

This isn't normal. Which size does your catalog have? 

Does your computer runs 24/7? But, a restart a computer is everytime a good idea.

You should quit Lightroom before you'll doing restart. In this case your catalog don't be corrupted.

Try to create a new temporarly catalog and import several (approx 1000+) pictures. The check the backup if it's faster. If yes, you can try to import all your images from the existing catalog. Maybe your recent catalog has a problem.

In a next step please check if your hard drive is heavily defragmented.

If you're on a Windows machine look here: Defragment / optimize your data drives in Windows - Microsoft Support

With MacOS I don't have any experience about this point.

Is your system up-to-date? Do you have installed all recent updates and patches for the operating system and the device drivers, especially the graphic driver. If you have a NVidia graphic card installed, make sure that you are using the recent Studio version of the driver, not the Game Ready version.

Please provide a copy of your 'System Info'. This can be get from the LrC Help > System Info menu item. There's a copy button in the System Info dialog. Press this button and paste the info into your next forum post. Please post all informations from the first line down and including Plug-in Info. All lines after the latest plug-in info can be cut off. 

You need to ask program questions in the forum for the program you are using
To ask in the forum for your program please start at https://community.adobe.com/
Moving from Using the Community (which is about the forums) to the correct forum