Backup MacPro

I would not recommend it. iCloud is more a syncing service than a backup service. If you want a cloud backup and/or sync service, then you may want to look at Sync.com. If all you want is cloud backup, then try services such as these:

Best cloud backup services - at a glance

• IDrive.
• OneDrive.
• Backblaze.
• Carbonite.
• CrashPlan.
• SOS Online Backup.
• SugarSync Business.
• Dropbox Business.

However, why even bother with the cloud, when you just need some external drives and backup locally. If you need access to your files everywhere you travel, then cloud services may make sense. On the other hand, if you just want reliable backups, then do it yourself.

Apple offers iCloud Backup for iPhones and iPads but not for Macs.

You can sync selected data to iCloud from a Mac (e.g., iCloud Photos, iCloud Drive including Desktop and Documents option) but while that has some advantages of a backup (and has the advantage of being offsite), it is not a backup. Major differences include the fact that you cannot sync everything on your Mac and also the fact that if you delete something, accidentally or otherwise, you have a limited time period (30 days in most cases) during which you can recover the data.

More information in:

Set up and use iCloud Photos - Apple Support

and

iCloud Drive FAQ - Apple Support

Basic Backup

For some people, Time Machine will be more than adequate. Time Machine is part of OS X. There are three components:

1. A Time Machine preferences panel as part of System Preferences;
2. The Time Machine application located in the Applications folder. It is used to manage backups and to restore backups.
3. Time Machine requires a backup drive that is at least 2-3 times the capacity of the drive(s) it backs up.

To use Time Machine you will need a separate backup drive formatted to use HFS+. This can be an HDD because speed is not that important for backups. The backup drive needs to be at least 2-3 times the size of the source drive. For a 250GB SSD, I would recommend a 1TB backup drive. These aren't too expensive. Visit OWC to see what your options are.

Your SSD can be formatted to use APFS, but Time Machine will not work with that format and should be formatted Mac OS Extended, Journaled.

Backups should always be made on a dedicated drive. If you have extra storage needs, then those also should be made on a separate drive. The Startup Drive should not be used for anything more than a startup drive.

Alternatively, get an external drive at least equal in size to the internal hard drive and make (and maintain) a bootable clone/backup. You can make a bootable clone using the Restore option of Disk Utility. You can also make and maintain clones with good backup software. My personal recommendations are (order is not significant):

• Carbon Copy Cloner
• Deja Vu
• SuperDuper! 

Visit The XLab FAQs and read the FAQ on backup and restore.  Also, read How to Back Up and Restore Your Files. For help with using Time Machine visit Pondini's Time Machine FAQ for help with Time Machine. This is an extensive site with most everything you may need for using Time Machine. You will not find a better resource for Time Machine in one location. Due to the passing of James Pondini, the site is no longer being updated. Therefore, some of the information may be a little outdated.

Although you can buy a complete external drive system, you can also put one together, if you are so inclined.  It's relatively easy and only requires a Phillips head screwdriver (typically.) You can purchase hard drives separately. This gives you an opportunity to shop for the best prices on a hard drive of your choice. Reliable brands include Seagate, Hitachi, Western Digital, Toshiba, and Fujitsu. You can find reviews and benchmarks on many drives at Storage Review. These same drive makers also sell external drive systems. These are enclosures in which they have installed one of their drives, labeled, and sell as standalone products.

Although you can buy a complete external drive system, you can also put one together if you are so inclined.  It's relatively easy and only requires a Phillips head screwdriver (typically.) You can purchase hard drives separately. This gives you an opportunity to shop for the best prices on a hard drive of your choice.  Reliable brands include Seagate, Hitachi, Western Digital, Toshiba, and Fujitsu. You can find reviews and benchmarks on many drives at Storage Review.

Enclosures are readily available. You can find only Thunderbolt 2 or 3 enclosures, only USB 3 or USB-C enclosures, and enclosures that feature multiple ports. You can find enclosures at places such as:

• Cool Drives
• OWC
• WiebeTech
• Firewire Direct
• California Drives
• NewEgg
• Best Buy

All you need do is remove a case cover, mount the hard drive in the enclosure and connect the cables, then re-attach the case cover. Usually, the only tool required is a small or medium Phillips screwdriver.