On a related note I just found someone local who has a
ton of used cctv 500gb sata drives for £5 each. I have a usb sata docking station
I could use them with more or less the same price as using blank dvd-r discs
for backups
I did this for a while. I have connections in the recycling industry and still work there occasionally because it can be interesting even if it's really hard work. So I basically could get hundreds of drives for cheap.
There were a lot of benefits. Read/write speeds being a massive one. Cost being another.
The problem is that the drives (at the time [circa 2005-2008] I was using a mix of 250 GB and 500 GB drives) are very bulky and after you get a few tens of them, VERY heavy.

Management and organization becomes a nightmare. Keeping redundant copies in case of a HDD failure also becomes a massive pain in the arse when you have 10's (not to mention hundreds) of loose drives lying around.
End result? After a few years of dealing with it, I went back to optical even if it was more expensive in terms of monetary cost. Now, I don't even deal with optical as I've had a few optical discs degrade on me which caused me to lose some invaluable data (don't duplicate data on optical discs created around the same time.

Try to use discs separated by a few years).
Now, for convenience I just use dual NAS enclosures which are mirrors of each other. While still possible to have a catastrophic failure that causes me to lose data, the chance should be relatively miniscule.
Not cheap, but I'd rather not lose invaluable data again.
Regards,
SB