Want to expand a mechanical hard disk, buy what model it

Mechanical hard disk on the buy Seagate, Western Digital, Hitachi these three brands on it, the hard disk to do the biggest is Seagate and Western Digital. Specifically buy what kind of have to buy according to your own needs, now the hottest is 1TB capacity hard disk, if you want to store a lot of things, then there are 2TB, 3TB, 4TB, 6TB, 8TB, 12TB and other capacity hard disk. If you buy a hard drive from Western Digital, don't buy a green disk, which has a lower performance, just buy a blue disk