Best external hard drive to store PC ripped music

Michael beat me to it, but I was going to suggest the OP get a RAID solution using it in Mirror mode. You would then have two or more duplicate copies of your music library. If one fails you pull the drive and replace it with a new one - the RAID system will automatically copy the remaining drive, creating a new duplicate. And so on. You can, of course, have more than one duplicate, but the RAID enclosure will become more expensive the more copies you have. They also tend to be more noisy than conventional drives (especially the cheaper models), requiring more cooling in larger housings. The other downfall is that this system does not maintain an off-site backup.

If you are simply looking for recommendations for external raw drives then Hitachi Ultra-Star's would be my pick. That said, any of them can fail, which is why back up is mandatory, IMO.

Drobo is much better, simpler, and easier than RAID, which I used to have.

I'm not sure I follow you here. Drobo is a brand. RAID is a technology. If you are using one of their arrays, AFAIK, that is just a mirrored RAID system. Not sure how it could be simpler than any other mirrored RAID system. The one I use requires no software at all and works entirely automatically. Two mirrored drives. If one fails a red light comes on and the other drive is put into use. Remove the bad drive, slide in a new one, and a brand new copy is automatically made on the new one maintaining a mirrored state. How is the Drobo array any simpler?

I had a RAID system for several years. I used one of our IT guys to set it up, and it worked very well. But, it is not simple, it is not plug and play as the Drobo is.

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Raid is much more involved.

The RAID you've had experience with using at work was using a higher level of RAID for slightly different purposes, using older technology. The more complex devices for industry do require some setup. Most of the reasonably priced mirrored RAID (RAID 1) solutions being offered currently are also plug and play (like DROBO's RAID units), are stone simple and can be treated like any other storage device with no complex setup. They are also very simple to swap drives in and out if one fails.