First, I wanna fuck SAMSUNG. It's a holy shit. The real world knows that. Plus, it screwed the hell outta me in every way.
Next, it's 'bout HITACHI. It runs too loud like an old Eddystone steam engine, but still better than SAMSUNG however.
Now, let's choose the right ones. Of course, they're; #1 for WESTERN DIGITAL (WD) & #2 for SEAGATE.
They're known for solidity & long life. They run smoothly without making horrible noises. They perform efficiently, saving your time as well as boosting up the speed of your computer work. They won't get you in trouble time by time like others. In fact, they're the best. Techies recommend 'em.
Formerly, MAXTOR was staying at #2, holding SEAGATE at #3. But, SEAGATE became #2 for the first time, after acquiring MAXTOR in 2006 & SAMSUNG in 2011. 
Wait! Is SAMSUNG now a SEAGATE one...? No. SAMSUNG is just a subsidiary of SEAGATE, but it's crappy quality is still maintained by itself. 
In 2012, WESTERN DIGITAL acquired HITACHI, so there's no HITACHI anymore. 
Actually, WESTERN DIGITAL & SEAGATE including TOSHIBA are the survivors of HDD world. But, no way TOSHIBA is worth considering #3, comparing to WESTERN DIGITAL & SEAGATE. So, there's indeed nothing at #3. 
Outta 'em all, I'd highly recommend you to buy WESTERN DIGITAL. When you buy a HDD, you should mainly consider 'bout its cache, cos the larger the cache is, the faster the HDD is. Therefore, WESTERN DIGITAL brings you its ultimate performer, WD BLACK (previously CAVIAR BLACK), that runs on 6 Gbps interface, with 64 MB of cache. The series is available from 500 GB to 4 TB.
Unfortunately, there are no official distributors for WESTERN DIGITAL or SEAGATE in Sri Lanka, but you can buy 'em at
TECHZONE or
BARCLAYS. I assure you that these are trustworthy places to buy all of your computer needs.
Plus, if you're deeply in need of WESTERN DIGITAL, then you can go to
WESCOM INFORMATION TECHNOLOGY or
WESTERN DIGITAL COMPUTERS (Don't be messed up with this name, as it has no relation to the HDD brand.), cos they're the non-official agents of WESTERN DIGITAL in Sri Lanka.
For WESCOM INFORMATION TECHNOLOGY & WESTERN DIGITAL COMPUTERS, I gave you the links of their official Websites, only to show you their contact details. Otherwise, not to show you the content, as those Websites aren't properly being maintained, therefore suffering from lack of info.
DISCLAIMER: I'm not a promoter for any of the above mentioned companies at all.
