Which do you think is better to buy for my archive hard disk - 1 terabyte or 2 terabyte? Mostly for storing pictures but that new hard disk can also serve as my backup master disk. I am thinking of buying 2 units of 1 terabyte so I can split the database. But the cost, it is more expensive than buying 1 unit of 2 terabyte hard disk.
If the 2TB disk is cheaper than two 1TB disks then it's better to buy the cheaper 2TB disk. You can then partition [there are plenty of tools which can help you do that] the disk into 2 or more partitions and store your pictures in one partition and anything you'd want to save in the other partition(s).
From a value standpoint, it's obviously better to go with the larger hard drive. For Windows 7 and 8, though, you don't want to exceed drives larger than 2TB because the system doesn't handle them well. If, for whatever reason, you needed 3-4TB or storage, it would be better to split things up. As Denis Hard says, you can partition the single drive to handle your needs.
I used to sell hard drives and worked for a couple of the main companies and most people find 1TB more than enough. On a price point, it can matter which brand you get as some people used to come in store and complain cheaper brands with higher storage amounts failed or were slow. They returned the products and bought a better quality one with sufficient storage rather than to buy more to save money. Most found it to be a false economy. Not all are made the same! I used to work for Seagate and WD.
If you can bear the cost I'd advise you to go for 2 disks of 1 TB each. I presume that your OS is windows. Indexing and handling a large amount of data requires a lot of processor power and your performance could drop as a result. Your OS will also use a lot of physical and virtual memory. I personally recommend making mirror images of your primary hard disk. So, even if one fails the other one will come in handy. Also, data retrieval is an expensive process. So go for two instead of one.
