Based on what you describe, you will need two sets of storage for your work - one set of drives for storing your content and some other medium to store a backup copy of everything.
Unfortunately, there is no 100% reliable external drive available, as there is always a risk that an external hard disk will fail, whether it is networked or attached externally. Hard disks can fail without any warning sign, one day without a glitch and the next day not being able to spin up at all.
If you can afford it, I would highly recommend going for dual HDD external USB (or NAS) drive that supports RAID1. This way if one hard disk fails, you can work as normal with the other until you get the failed hard disk replaced. Note that RAID1 is not the same as keeping a backup, since as both hard disks are constantly mirrored, if you accidentally overwrite any important file or end up with a major file system corruption, it affects both HDDs simultaneously.
For your backup, you can choose between going for another external 1TB HDD, optical media (DVD, Blu-ray, etc.) or tape. Here’s the pros and cons of each from my experience:
[B]Another external HDD as backup:[/B]
[li][B]Pros[/B]: Handiest to use, as it’s quite simple to do a periodic mirror or incremental backup of your files to it. Quick to search for files to recover, as you’ll likely only need two external HDDs. [/li][li][B]Cons[/B]: In the unlikely event that it fails at the same time as your original fails, you lose everything. If left plugged in and a major power surge occurs (e.g. near-by lightning strike), both the original and backup are zapped. Hard disks are fragile and a fall on a hard surface can permanently destroy its content.[/li][/ul]
[li][B]Pros:[/B] You back up to media as you need to. Each disc can be labelled, so you can search for past work just by looking at the discs, assuming they are stored away and organised properly. Safe from power surges, since they have no electronics. If one disc fails, you only lose that disc. [/li][li]Cons: A bad batch of recordable discs can result in the lot becoming unreadable (although no worse than a backup HDD failing). In the event of a major data loss, recovery from disc after disc will be a tedious process.[/li][/ul]
[li][B]Pros:[/B] You can either do a full or incremental backup. Tapes are generally fairly cheap per gigabyte, so they are cheaper to store multiple backups. Like optical discs, they have no electronics, so cannot be damaged from a power surge. Tend to be more reliable than optical media (from my experience with DLT tapes over the years.) A full recovery is fairly quick, a lot quicker than restoring from a large set of optical media. [/li][li]Cons: A tape drive is very expensive to purchase, especially large a capacity model. Recovering individual files can be a very tedious process (several minutes for a set).[/li][/ul]
A better backup option, again if you can afford it, is to use a combination of backups, e.g. make your backup to disc (DVD, Blu-ray, etc.) as well as to a second external HDD.