Back in the 1980s there was a straightforward and clear divide among HDDs – stepper-motor drives were for consumer applications (cheap, slow, temperature‑sensitive and somewhat unreliable), with voice-coil drives for enterprise use (expensive, fast, temperature‑compensating and much more reliable).
With the advent of embedded servo technology, though, the cost penalty came down and around 1990, voice-coil drives became affordable for everyone.
From here the distinction between “consumer” and “enterprise” drives was defined less by technology than by interface (ATA versus SCSI); the fastest, hottest drives came out in SCSI first and trickled-down to ATA after a few years. Faster-spinning ATA drives were generally well-made, slower models cheaped-out somewhat.
By 2000–2002 there were four or five spindle speeds with associated “tiers”: 4400rpm or 5400rpm (consumer), 7200rpm (nearline), 10,000rpm (high performance) and 15,000rpm (top end). From this era, the 7200rpm nearline models are generally most reliable – the 10K and 15K being very-stressed by their frantic spinning and abrupt seeks, while 5400rpm models were cheaped-out to varying degrees. Samsung was a notable exception in also making their 5400rpm drives to nearline standards (being a conglomerate with the luxury of sacrificing profit margins), while Maxtor had an interesting split in their 5400rpm line-up – the D540X was nearline, whereas the single‑head‑only 541DX and Fireball 3 were among the lowest-of-low-end consumer rubbish.
It was still a bright time though – Seagate’s Barracuda ATA line achieved SCSI performance from the first generation and SCSI reliability (and then some
) from the fourth generation on, with only the interface barrier still keeping the ATA and SCSI Barracudas apart (which Seagate mitigated by also adapting the Barracuda ATA III & IV into the Barracuda 36ES & 36ES2, respectively, for the upgrade market). The emerging SCSI-derived Serial ATA interface promised to resolve this divide, and after testing the waters with the Barracuda SATA V, the two Barracuda lines finally united into the Barracuda 7200.7.With the cost difference between 5400rpm and 7200rpm drives shrinking to almost nothing (and Seagate discontinuing their consumer 5400rpm U6 series soon after releasing the 7200.7), people were happy to use 7200rpm drives as standard and finally have enterprise-quality HDDs as the norm everywhere
…it's just a pity this was so soon after IBM shot themselves in the foot (yet again), by first making the Deathstar 75GXP/40GV and 60GXP (and debatably 120GXP), then obstinately replacing them with more of the same and flatly denying any blame. IBM retroactively claimed a runtime limitation of 8 hours/day, which didn't get them out of the class‑action lawsuit but did stir up FUD and cemented the biases of many sad simpletons who assumed SCSI drives were unilaterally more reliable than ATA models. (Ironically given the bulletproof reliability of the Barracuda ATA IV/V and 7200.7, Seagate's own Cheetah 10K.6 was not so durable – largely due to clinging to already‑obsolescent BB spindle motors, although it's worth noting smaller details such as an aluminium voice‑coil and bare copper PCB lands; whereas the Barracuda ATA IV through 7200.10 all have copper coils, and the ATA V and earlier have HASL-finished PCBs which was begrudgingly changed to immersion-silver on the post-RoHS models. The Cheetah 15K.3 had FDB so should outlast the 10K.6, but my money is that it still won't beat the Barracudas.)
Maxtor promptly cashed-in on the post-Deathstar FUD by introducing the “enterprise grade” MaXLine Plus II and MaXLine II; needless to say, they were no better than the “consumer grade” DiamondMax Plus 9 and DiamondMax 16, and all were far more failure-prone than the Barracuda 7200.7 (which promptly matched their 5‑year warranty by late 2004). Despite Seagate’s confidence and track record, though, the FUD was too widespread and entrenched to defy altogether; after Western Digital released their “RAID Edition” drives, Seagate too gave in by late 2005, giving the Barracuda 7200.8 an “enterprise” variant under the NL35 moniker.
To Hitachi’s credit, they did most of the right things to rejuvenate the Deskstar brand – since ≈2006 they gave an explicit 24×7 rating in all Deskstar datasheets.
(Though they never truly cleared the air; they should really have apologized for IBM Storage's black lie.)
In the end, Seagate bought Maxtor; and one way or another, Maxtor seemed so miserable (about Seagate striving to foil their ploy) that they worked to drag Seagate down to their own level. If the Maxtor employees deliberately took revenge on Seagate, we may never know; but one thing's for sure – even if I got an ST3000DM001 for free, I'd rather trust a RAID 0 of however many 7200.7s it takes to match the capacity
(It'd be a lot faster too 
)And in peddling such low-quality drives as the ST3000DM001 or ST1000DM003, Seagate also dragged Western Digital down to their price points – modern WD Blues don't last that long either (according to c_hegge etc.), which is why I went with the Caviar Blacks in 2014 (nowadays you just get an Ultrastar or so).
To really convey just how far back we've slipped – the better late-1990s drives were already quite reliable (I have several Quantum Fireball EL/EX/CR in good health), and even early-1990s models had a fighting chance. To find an era when HDDs were generally as unreliable as the ST3000DM001, I guess we have to go back to the 1980s again; the days of the MiniScribe 3650 and Seagate ST‑277R, and those horrid Tandon-derived Western Digital steppers.
