The cheapest and all around best method for storing large amounts of data is pretty obvious... desktop computer hard drives, hands down. (i.e. SATA 3.5" internal hard drives)I would recommend at minimum two separate hard drives with one copy of your data one one of them and another copy on the other as that should give you reasonable protection against data loss (which is pretty much what your doing, just slightly different, but basically the same). plus, to lower risk... try not to have one of those drives connected to your computer much outside of transferring the data and then disconnecting it not long after as this should help minimize the risk of a virus getting to it should it take out your computer data etc, it probably won't get to the external hard drive if you don't leave it connected to the computer much in general besides for a quick data backup and then disconnect it. basically just get a external docking station as this allows you to connect pretty much any (well, at least up to 8TB on the one I have along with another device I got(both are USB 3)) standard SATA based internal hard drive to it be it 3.5" or 2.5". these will probably run you somewhere around $20 for the device to connect a internal hard drive to your computer externally using a USB connection.
so if you don't have a computer to use them in etc you can get one of those external docking stations that use a USB 3 connection to get full speed out of the drives because if your only using USB 2, which I suspect most computers only have this, especially if they are a bit older, you will be capped to about 30MB/s transfer speeds (i.e. which comes out to about 108GB per hour of data transfer) when modern hard drives can go well beyond that (like 3-4 times as fast, if not faster) but with USB 3 connection your hard drive will go as fast as it possibly can when transferring files to it as you won't be capped by the USB 2 interface but by the devices your reading and writing data to which is what you want as it won't handicap your hard drive like USB 2 will. but anyways... if your not sure if you got USB 3 or not, just look for a BLUE color USB connector on your computer. if you only see black ones they are USB 2(unless you got a ancient computer it could be USB 1 which is dead slow (I think around 1MB/s), but I doubt there are many computers still in use that are THAT old), if they are BLUE in color, they are USB 3 etc. that should get the gist of it across. because if your computer only has the older USB 2 (black color) connection you will have to likely buy a USB 3 PCI-E expansion card (which is what I did to add USB 3 support to my computer since it only supported USB 2 on the motherboard itself) to add USB 3 support to your computer (I am assuming you got a desktop) or just deal with the slower speed (i.e. 30MB/s tops) which will make transfers of large amount of data take quite a bit longer since it's going to be something around at least three times as slow which means it will take 3 times the amount of time at the minimum (which is a lot of time when your transferring 2-4TB of data etc) as it's likely any 4TB+ range hard drives will crack at least 90MB/s or faster and likely a good amount beyond this as I am being conservative here in the 4TB hard drive transfer rates but if it's running on a USB 2 connection it will be capped to about 30MB/s given that's the limited of the USB 2 interface and there is simply no way around it unless you have a USB 3 port on your computer AND use a external hard drive docking station etc that supports USB 3 as once you get those the hard drive will be able to run at maximum transfer speeds.
but taking a quick look online you can get a 4TB (i.e. 4000GB) hard drive for roughly $100 give or take which are reasonably priced as I figure as a general guideline for buying hard drives (or even SSD's) is not to exceed about $120-130 range tops per hard drive because usually in terms of bang-for-the-buck around $100 or so is the sweet spot in terms of giving you maximum storage space for a reasonable price. but if your a little low on cash and don't have too much data to store you can get a couple of 2TB hard drives for about $100. hell, taking a quick look on the site I got my Hitachi 2TB hard drive from they are currently cheaper than usual, only $40 ($39.95) for each 2TB hard drive and free shipping (assuming your in USA). only small catch is... it only comes with a 1 year warranty (your typical hard drive the last I checked is 2-3 years warranty) and it's just the drive itself with no SATA cable included. but it's worth the gamble at that price as they are new and seem to be solid drives as I have one of them. or look at it this way... you can get two 2TB Hitachi drives each with a one year warranty for basically $80 or get a single hard drive with a 2 year warranty for about $60. in my opinion... the 1 year warranty drives are the better choice overall as you getting twice the storage space for only $20 more (or the same storage (2TB) for about $20 less
) than just a single 2TB HDD with the 2 year warranty. so it just depends on your budget as I feel those $40 2TB hard drives are a solid choice for one trying to keep price minimal but still get a good chunk of storage space (i.e. 2TB (2000GB)). in my opinion... it's not worth buying 3.5" hard drives any smaller than 2TB anymore as the 2TB or 4TB (maybe a little bigger) is pretty much your all around best choices for reasonably priced drives that won't break your bank but still offer plenty of storage space. but as storage space needs increase... it's probably better to stick to 4TB and larger drives but it depends on your situation and would you rather have separate drives so if one fails you still got another or would you rather have more space on a single drive so it takes up less physical space etc. or put it this way, to give you a general idea of how much data a 2TB hard drive can hold (which is not a large hard drive by today's standards)... if you got a bunch of video files that averages 7GB each, that gives you roughly 285 video files on a 2TB hard drive. or even if you go up to say roughly 10GB average for the video files (which is pretty large) that's about 200 video files on a 2TB hard drive (or 400 video files on a 4TB hard drive).
another thing... assuming your sticking to more current hard drives, based on some 'backblaze' data in a study a while ago, HGST hard drives tend to be one of the more reliable hard drives. but... they do tend to cost a bit more (but usually come with a little longer warranty to(3 year instead of 2 year the last I checked)). but here is something a bit more recent from backblaze hard drive study to give you a general idea on hard drive reliability...
www.backblaze.com/blog/hard-drive-stats-for-2018/
or another option, depending on how much data you need to store and what level of sensitivity it is, you could store some of it online as a alternative/additional backup source. but anything of higher importance security level stuff I would not backup online as it's just not worth the risk but in terms of stuff you would rather no one see but if they did get a hold of it, it would not be that big of a deal you could simply encrypt the data before uploading to a random online storage place etc as that should keep anyone from viewing the data. but I would not store anything too sensitive online as a general rule like say passwords for websites you use etc as it's just not worth the risk if the site your uploading it to is compromised as I would just make local backups of that sort of stuff and put it somewhere safe.
with all of that said... given what you told me that should give you a reasonable level of protection against data loss but I would suggest keeping that 'one sole drive as the backup' externally on say a USB v3 hard drive docking station as this limits exposure of it being taken out if a virus happened to hit your PC.
NOTE: I noticed many people tend to ignore backing up important data until it's too late and then reality sits in and they lost important data and it sucks for them. I know we all can be a little lazy in this regard but doing my general two hard drive thing should be a bare minimum for people if they even slightly care about the data as this way it will protect against most hardware failure data loss scenarios as those people who have only one sole copy of important in say their phone or laptop are just asking for trouble and will likely get burned eventually.
p.s. but for that 'cannot afford to lose kind of data', which is typically family pictures/videos and the like, I tend to do the general two hard drives thing along with at least one backup on a quality DVD recordable disc (I tend to make two copies, one on Verbatim and one on Taiyo Yuden as this way the odds of both of those dying at the same time should be pretty slim). I recommend using only Verbatim or Taiyo Yuden brands since they tend to be the most reliable over the long run (there might be some other decent brands here and there but given Verbatim DVD 100 packs are about the same in price or not much more than other brands, it's not worth gambling with other brands) and are reasonably priced but Verbatim is the easier to recommend of the two because they are generally cheaper and are of similar quality even though Taiyo Yuden are probably a little better but tend to cost more. either way, you can't really lose going with either brand but since Verbatim are generally cheaper that's sort of the default choice for many. but anyways... using that method I am pretty well protected against data loss short of a house fire etc. but the reason I generally don't suggest DVD for backing up data much anymore is because years ago hard drives became overall better in that they give you more storage space per dollar spent (and not to mention hard drives are easier (and less time consuming) to work with). so while in terms of $, burning DVD data backup is generally not worth it, I think it's worth the price premium for that 'can't afford to lose kind of data' especially if your not burning boatloads of DVD's as a 100 Verbatim recordable discs (which are 4.7GB each disc) will allow you plenty of family photo etc type of backup and your looking at $30-ish tops which is a small price to pay for peace-of-mind in combination with the hard drive backup copies etc. or if you would still rather avoid burning DVD's... I would seriously consider at least three copies of higher importance data on three difference devices (like say three hard drives or two hard drives and say a USB memory stick etc) as that should put the chances of losing that data to a minimum short of a house fire etc. but one could possibly opt for uploading stuff online if you don't have too much data to backup etc.
like for example... the last I checked I seen some 2TB (i.e. 2000GB) hard drives for $50 online and a 100 pack spindle of Verbatim DVD recordable disc will run you anywhere from around $20-30 which is only 470GB of data (at best) and not only that transferring data is MUCH faster using a hard drive as the hard drive is much more convenient. so as you can see, outside of some select situations, a hard drive is just flat out superior almost across the board even though I think DVD's have their advantages over hard drives to some degree like you ain't got to worry about accidental data loss (from deletion etc) and I would tend to trust those more than hard drives for long term storage, say 10-20+ years down the road. but another potential negative with recordable DVD discs for data is that I suspect there will eventually come a point where, even assuming the discs themselves last a long time, there might eventually reach a point (say maybe 20-ish years from now) where finding DVD drives to read those discs might become a bit more scarce etc (which could be a problem because even if your recorded DVD's last 50-100 years, it's not going to matter much if you don't have a way to retrieve the data to use it when needed). still, I think recordable DVD's are solid reliable backup of higher importance data backup for say the next 10, maybe 20 years or so as I suspect it won't be difficult to still find DVD burners/readers over the next 10, maybe 20 years or so. so while they tend to be slower for writing and reading data, I tend to have more confidence in long term reliability in quality recordable DVD's over many other data backup options out there as I have a fair amount of Verbatim branded (and some Taiyo Yuden) DVD recordables that are about 10-15 years old and still work well (I might even have some CD-R's from around 1999 or so here and there to).
Whoever suggested that does not know what they are talking about if getting maximum storage space for the least amount of $ is your primary concern.
about the only time USB flash drive (and the like) might be okay is if you don't have too much data to backup and want something portable/convenient. but even in these cases, unless portability is paramount, one could possibly opt for a external 2.5" hard drive which many can be powered straight from the USB port with no additional power required unlike regular 3.5" desktop portable hard drives which will require a external power source as the USB port simply cannot supply enough power to power these solely from the USB port. but again, 2.5" hard drives typically give you less storage space, and cost more, than a regular 3.5" desktop drive. but here your basically trading more $ for more portability/convenience.
p.s. but personally... while hard drives can and do fail (along with just about every other kind of storage out there), I would tend to trust them over a USB flash drive in general with my important data. with that said... I don't think there is any real 'proof' as to whether hard drives are more reliable than USB storage or not but I just tend to trust platters (in a hard drive) over a memory chip as it seems like a memory chip can be more flaky to where I suspect it's easier for those to die out of no where vs a standard hard drive.
on a side note... personally I have only had two hard drives die on me (pretty much) which is a old 40GB IDE and a old 80GB IDE. hell, I have had more PSU's (i.e. power supplies) die on me than hard drives when I would expect hard drives to be more problematic in general than PSU's over a wider range of people. but anyways, after my generally somewhat bad luck with PSU's, I made sure to get one with a longer warranty (i.e. 5 year warranty) which I had since Nov 2012 which makes it the longest lasting PSU I ever owned as it's 6 years and 4 months old and still going as it had a 5 year warranty which ended Nov 2017. it's a Seasonic brand which, the last I heard, are one of the most reliable PSU's in general. if I can get at least say about another year out of it, it will be my clear cut best PSU I ever owned even though strictly by how long it's lasted it's my #1 already AND I pretty much leave my computer on all of the time to short of occasional power downs etc. but in the past it seems the PSU's that died on me failed within about a year-ish of the end of the warranty period of which my previous two PSU's had 2-3 year warranties on them and the one with the 3 year warranty, which I first got back in March 2006, was not cheap either as I think it was something around $120 at the time. the current Seasonic I got for around $70-80 I think of which the prices of these came down since I got it in Nov 2012 as that general same one is roughly $40-60. hell, I got a great buy on a Seasonic 430watt PSU on Ebay for only $22 which I got lucky as the guy selling it wised up and not long after they where listed they quickly sold out and now that same guy is listing them for $40 which is about what they are worth. but I got that in my backup computer currently as if my main PC's ever dies ill probably just temporarily swap it out in my main PC which will save me a bit of $.
That's about what I consider a minimum level of protection against data loss, as even for people who are lazy, what your doing there is basically a bare minimum with the two total copies of the data on two different devices scenario as this is probably 'good enough' to protect against data loss from random hard drive failures which are probably the most common way someone would lose data (assuming one does not get their computer infected with a virus and the like). those people who only have one total copy of their data sitting on a random device are just asking for trouble.
but your risk should not be too much assuming you check the 'one big unit' occasionally to see if it's still in good running order and I would probably avoid having that 'one big unit' being always connected to the computer as, liked I mentioned in my novel above, will help minimize it's exposure to potential viruses you might stumble into that could mess up your data. like say you got hit with some ransomware and it screwed all of your hard drives except that 'one big unit' that you don't have connected since it's sitting somewhere else in your house strictly for backup, you will be really happy it's not always connected to the computer.
NOTE: you can use a free program like... 'Crystal Disk Info' (i.e.
crystalmark.info/en/download/#CrystalDiskInfo ; just use the 'standard edition') to check SMART info of a hard drive as it can be a indicator of early failures etc and it will usually show how many hours it's been powered on and can tell you if a hard drive has some bad sectors on it to which can be a early indicator of potential drive failure. so while there is no way to accurately predict how long your hard drive will last, that program can be of some use. but out of all of my hard drives that I have that still basically work, two of them have some bad sectors on them but I don't store anything too critical on those drives and they are mostly retired at this point anyways as they used to be in my main computer powered on pretty much all of the time but not anymore. but one of the two drives I got some data, as a backup copy, that I would rather not lose and in this regard after transferring the backup data copy to it, I ran a check on the data to make sure it was intact (like checks out as the same as the original) before putting it away in storage so it will probably be okay for a while to come should I ever need it.
) than just a single 2TB HDD with the 2 year warranty. so it just depends on your budget as I feel those $40 2TB hard drives are a solid choice for one trying to keep price minimal but still get a good chunk of storage space (i.e. 2TB (2000GB)). in my opinion... it's not worth buying 3.5" hard drives any smaller than 2TB anymore as the 2TB or 4TB (maybe a little bigger) is pretty much your all around best choices for reasonably priced drives that won't break your bank but still offer plenty of storage space. but as storage space needs increase... it's probably better to stick to 4TB and larger drives but it depends on your situation and would you rather have separate drives so if one fails you still got another or would you rather have more space on a single drive so it takes up less physical space etc. or put it this way, to give you a general idea of how much data a 2TB hard drive can hold (which is not a large hard drive by today's standards)... if you got a bunch of video files that averages 7GB each, that gives you roughly 285 video files on a 2TB hard drive. or even if you go up to say roughly 10GB average for the video files (which is pretty large) that's about 200 video files on a 2TB hard drive (or 400 video files on a 4TB hard drive).
