How long does the first cloud backup take?
Budget days, not hours: the first backup uploads everything, and home upload speeds are the bottleneck. At a typical 30 Mbps upload, 500 GB takes roughly two days of continuous running. IDrive can ship you a physical drive to skip the wait; after the first pass, only changes upload.
The math nobody warns you about: upload speed, not the backup service, sets the pace. Divide your data by your connection's upload rate (the small number in a speed test) and the truth appears: 500 GB at 30 Mbps is around 37 hours of saturated uploading; a 2 TB photo archive on the same line is closer to a week. Backup clients throttle themselves politely by default so your video calls survive, which stretches it further.
Make it painless rather than fast: start the backup before a weekend away, let it run overnight indefinitely (the clients resume automatically), and check the apps' settings for "performance" sliders if you want to dedicate more bandwidth. The structural shortcut is physical seeding: IDrive Express mails you a drive, you copy data locally and mail it back, and your first backup happens at parcel speed instead of DSL speed, free once a year on most plans.
The good news is that this is a one-time toll. After the initial pass, backup clients upload only new and changed files, which for normal use is minutes of background traffic a day. The first week tests your patience; every week after that, the system is invisible.