I just experienced my first hard drive failure. Here are some lessons learned:

1) Backup, backup and check your backups. I had most of the drive backed up to the cloud, in two different locations, but due to a rebuild/reconfiguration of my computer, it turned out that I had not been backing up since about January. Fortunately, I discovered a version of the files (the jpgs; raws are lost) for all but one of the shoots

2) Newer spinning disk drives have helium rather than air inside, to allow closer spacing of drive platters. The problem is that if there is mechanical failure (what I experienced), it's virtually impossible for a drive recovery service to get the data back.

3) Because of the helium technology, it may be the case that older drives will fail due simply to age--some of the research that I've done suggests that the helium will leak over time. So there may be a hard limit in terms of local backup if you use that kind of drive.

Oh, remember to backup your files!

Ancient wisdom: there is no such thing as too many backups. Even more ancient wisdom: there are only two kinds of hard drives, ones that have crashed and ones that are going to crash.

I have four failed Seagate external backups that have less than probably 20 hrs operating time each on them. I contacted seagate and they offered to recover one of them if I sent it in 30 days which I failed to do. Regardless I just want to share my experience with Seagate, btw I am extremely delicate with these devices as I am with most of my equipment. So if you are shopping for hard drives be warned. Surprisingly they bought Lacie which offers a five year warranty "and" recovery with their desktop HD's.

My setup:

Redundant RAID system that is backed up into the cloud every night. Backup of a backup of a backup.

I think the IT rules for backup applies, if they are photos worth saving.  3 full backups, 2 different media types.  1 offsite location.  It's expensive,  but it prevents a lot of heartburn.

Former IT person.
I use Dropbox but also burn images to Blu-Ray and a set stays in safe deposit box.

Not a question of "If" more a question of "when"
Just like peeps we are all gonna die one day

Back in 2012 I lost the entire year's worth of images due to hard drive failure (with RAID setup - Thanks, Mac, Lacie, and Seagate).  Backing up the backups' backup backups isn't just a case of needless effort and overly cautious paranoia, but an absolute must.   Yes, multiple media; multiple copies.  And even then...