The opposing virtues — whatever they're worth
As we know, the two remaining HDD majors have opposing marketing strategies: Seagate trumpets “The Power of One” while Western Digital promotes “The Power of Choice”. The problem with them is that neither company balances them: Seagate misses some of the desirable choices (their current desktop drives come only in 7200RPM up to 3TB, and 5900RPM in 3TB and 4TB versions), while Western Digital has extraneous product families — and, funnily enough, so does Seagate!
To elaborate…
“Nearline” drives (Seagate NL35/Barracuda ES/Constellation CS and ES; WD RAID Edition; Maxtor MaXLine)
Essentially these are desktop (S)ATA drives, but with more rigorous factory testing (to reduce ‘infant mortality’ rates), TLER (time-limited error recovery), longer warranties and, in newer models, a SAS interface option. Indeed, Seagate's Barracuda ES.2 failed in exactly the same way as its desktop counterpart, the infamous Barracuda 7200.11.
But to be honest, if I'd be uncomfortable with drive X in a (not overly performance-critical, of course) server (or at least a NAS unit), I wouldn't use that drive for anything even vaguely important. I've read that some earlier Western Digital Caviars (non-RE), at least, could be TLER enabled, so clearly the only reason for the RAID Edition is money, money, money (for Western Digital, that is).
Of course, it was ironic that Maxtor, the first to differentiate between “desktop” and “nearline” drives, was decidedly below-average on the reliability front.
(For the record: I would have happily used Seagate Barracuda ATA IV/V or 7200.7, or the FDB-equipped WDs that came a bit later, in a 24/7 role; and I'm sure that many others have done so without problems. Seagate even recommended the Barracuda 7200.7 for nearline storage, back in the day. 
)“A/V” drives (Seagate U-CE, DB35, and Pipeline HD; Maxtor QuickView; Hitachi CinemaStar)
Well, there were HDDs (most of them high-end SCSI enterprise models, such as Seagate's original Barracuda) in the distant past that stored the servo information on a dedicated media surface and the user data on the others. As explained on the old PC Guide, many of those drives had to recalibrate periodically to account for thermal expansion/contraction. But that was ages ago.
Since then we got the ATA Streaming Command Set (which allows supporting devices to skip extensive error recovery on audio/video streams to avoid record/playback interruptions), but I fail to see a justification for limiting its support to “special” drives. No manufacturer that I'm aware of made separate physical designs for these drives (to do so would incur pointless expense), so they were basically just firmware swaps of their “desktop” counterparts. (Not that the feature was ever mandatory — you can do without it for a small number of streams.)
Also, Seagate's DB35.4 and Pipeline HD (all generations except the Pro) are supposedly more heat-resistant than the Barracudas they were based on, as Seagate says they can withstand 75°C (the normal limit being 60°C) — but how?
Other possible points of differentiation:
- Seek modes — obviously, for a drive used solely to store audio/video or game saves you would want it to seek as quietly as possible, whatever the increase in access time (as long as it isn't something outrageous like >200ms). For a heavy-duty server you would want the fastest possible seeking, and for desktop PCs a balance would be most desirable. Of course, configuring it is what AAM was for — too bad Western Digital recently followed Seagate in abandoning it (presumably because of the patent trolls, or perhaps to save on firmware development costs).
- Spin-up power — for the entertainment devices and multi-drive servers or NAS, this should preferably be relaxed to limit audible whine and PSU loading (respectively). For a portable drive, more aggressive spin-up may be desired so the user doesn't have to wait so long for the drive to be ready. I suppose it would be possible to install a switch (or failing that, jumpers) on the logic board to choose between ‘quick’ and ‘slow’ spin-up if desired, though.
Anyway, technobabble aside, as was said in the old PC Guide:
You may still find companies trying to sell "special A/V drives" at higher prices than regular drives. These days, this is more likely to be an attempt to get you to part with a greater percentage of your wallet than anything else. It's not necessary to look for such designations on modern drives.
Well, certainly a cleverly disguised attempt. Then again, the price competition in the high-tech industry is too fierce for its own good, so…
“NAS” HDDs (WD Red series and Seagate's…well, NAS HDD)
Well, I'll quote WD's marketing and test it against the truth:
3D Active Balance Plus
Our enhanced dual-plane balance control technology significantly improves the overall drive performance and reliability. Hard drives that are not properly balanced may cause excessive vibration and noise in a multi-drive system, reduce the hard drive life span, and degrade the performance over time.
Not properly balanced?! OMG!!! Don't buy those “ordinary” drives!
But for what it's worth, most of the drives in my current collection have reasonably well-balanced spindles. (The three Barracuda 7200.10s are a notable exception; the Barracuda ATA IVs and 7200.7s were better in that regard.) Rotational vibration (RV) sensors are certainly good to have in a system with a large array of drives, but are unlikely to be needed with 2 or 3 drives that were decently balanced in the first place.
Experienced in NAS
WD Red is a reflection of the most extensive NAS partner compatibility- testing list that is available on the market.* That means when you buy a NAS enclosure, you can trust that WD Red will be the most compatible drive available. Our pride is in our product and our vision is shared with our customers.
As far as I'm aware, there were only ever a handful of incompatibilities with HDDs (aside from the capacity barriers). So that's nothing to brag about.
The sub-page on NASware shows a thermal comparison of the WD Red with a 7200RPM drive — well, they didn't even try to hide that it's a Seagate, probably a 7200.14. That the Seagate gets hotter is no doubt true, but that has nothing to do with NASware anyway — it's simply because higher RPM = more heat (always has, always will). Of course, that section also appears on the page for the recently added 7200RPM “Red Pro”, which doesn't even begin to make sense.
Seagate has also added a 7200RPM offering (called the “Enterprise NAS HDD”) to their range, for what that's worth.
(Back in the good-old days, though, they did recommend the Barracuda ATA IV/V and 7200.7 for NAS applications.
)In summary, there are two types of market segmentation: natural and artificial. In the case of HDDs, the natural type would include spindle speed and form factor options (that can't be changed without a complete redesign), while ‘firmware swaps’ (e.g. between desktop and CE drives) are artificial; the other stuff (miscellaneous enhancements and, at least in the past, buffer size options) presents a grey area.
One other partial justification for the market segmentation may be optimizing the drive firmware for different access patterns. But I suppose they could provide user-switchable modes where needed, although it would increase the total size of the drive's firmware a bit (but I think we can handle that). Besides, whether or not they even bother with separate optimizations for each “version” of the drives is uncertain (it's known that the Barracuda 7200.9 and 7200.10 had the same server-optimized – but ill-suited to desktop computing – firmwares as NL35.2 and Barracuda ES.1).
Anyway, logically, I would go with the following HDD categories:
- A 5400RPM 2.5″ drive for entry-level notebooks, and small bus-powered USB drive enclosures. (Maximum peak current draw of 0.9A for USB 3, or 0.5A for USB 2.)
- Maybe a 7200RPM 2.5″ drive for better notebooks (but SSDs may take over before too long).
- A low-cost 5400RPM 3.5″ drive in the full range of capacities — for cool and quiet bulk storage in undemanding applications (e.g. DVR, back-up and archival, entry-level NAS, bulk data in systems booted from SSD), and perhaps entry-level desktop PCs. High-capacity models may have RV sensors.
- A faster 7200RPM 3.5″ drive in moderate capacities (1 to 2 or 3 disks?) — for mainstream desktop PCs and entry-level servers. (Older mainstream drives like the Seagate Barracuda ATA IV/V and 7200.7 fit this description nicely.)
- Maybe an up-market 7200RPM 3.5″ drive in very high capacities, with RV sensors, reinforced spindle, and a 5-year warranty — for high-end desktop PCs and high-capacity servers. (Rather like Hitachi's 5-disk flagships.)
- A thicker, higher-capacity 7200RPM 2.5″ drive for high-density nearline storage and SFF PCs.
- And, of course, the 10K and 15K, low-to-medium capacity 2.5″ drives for high-speed servers. I guess these will be the first category to go.
Of course, it's uncertain how much longer HDDs will remain viable in the face of silent and increasingly fast SSDs (which are fast catching up on capacity).
For what reason does Western Digital need a total of 17 drive categories, anyway? (This is including their Black² 2.5″ SSD/HDD combo, and the Scorpio Green extended-capacity 2.5″ drive. And, of course, the VelociRaptor.)
