taichi wrote:Do you have any knowledge about that drives reliability? To me, reliability is the most important criterion.
If I have any knowledge (I guess you mean not only
belief, but actual, statistically justified
knowledge) of the reliability of different mechanical 2.5” SATA HDD's? Unfortunately, no; I wish I had… bit I am doing as you do; reading user-reviews, reading tests, digging around.
It is obvious that the HDD manufacturers themselves are not publishing the failure rate of their different products; they keep this very secret for business reasons. Therefore, unless you happen to work for the QA Dept. in a very large corporation that use many (1000+) of different manufacturers various 2.5” HDD’s (or if you work for a large service organization that repair
many laptops!), and because of this you have access to a *large* amount of independent statistical reliability-data, I don’t believe you can find out which drive is better or worse, from a reliability point-of-view. And even if you could, there may be bad batches of drives from time to time, owing to e.g. faulty components supplied by sub-contractors. So… it's simply very hard (impossible?) to be 100 % certain that you have a high-reliability, guaranteed long-time, perfectly functional HDD. If you are therefore really serious about backup, you would probably want to look to streaming tapes, “cloud”-solutions, and of course keep several identical backups, stored in different places. Burn vital data (family photos e.g.) to DVD's, burn several DVD's (on high-quality media, with high-quality burners), check them, store them *SAFE* several places etc.
Anyway, about the reliability-information of e.g. 2.5” HDD’s that we believe we are able to dig up ourselves:
If you see the user-feedback ("review") on Newegg for the drive that you are mentioning in your first post; the
HGST 0S03694, you will notice 3 out of 16 users are reporting dead or defective drives... and that (3/16) translate to a catastrophic failure rate of 18.75 %

This cannot be the truth; it simply can’t be that bad; it does for sure not represent a large selection of these drives.
Moreover, to be able to better interpret user-reports, and to be able to make better choices yourself, it is useful to know the basics about reliability in electronic equipment; incl understanding the mechanisms behind "infant", "burn-in", and "wear-out" types of failures... see e.g.
Topic: Electronic/Electrical Reliability. What is actually important for you; "infant", "burn-in", and "wear-out" errors? All, of course, but they are not equally important (wear-out must of course be expected!), but consider what is reported in user-reviews probably most often posted relatively short after some item is bought? Read user-reviews in this light, and decide what's important for you.
Now, as we know, most happy costumers/users don't come back to give positive feedback; costumers of course expect that the items they buy works as advertised (... or most people are probably simply too lazy to give feedback!), so this 18.75 % failure rate cannot be expected to cover a population of, say, 10.000 of these drives. In the user-feedback for the same drive on
Amazon things look much different, and by a first glance much better, but
Hey! you
always have to be very critical with Amazon's reviews... because they group (= show!) review of
different sized drives (e.g. 500 GB and 1 TB drives) under
both of the products; see e.g. the user-feedback
By Henry Dumanian (Hicksville, NY), entitled: “New cable” and posted January 3, 2015 which is for a
HGST Touro S 500 GB drive, but is actually listed (= shown) in the reviews for the HGST Touro S
1 TB drives (0S03694), that you are making reference to. The actual HDD's inside these two HGST backup drives are obviously very different (500 GB vs. 1 TB) and may, or may not, be of different product families; you have simply no idea of what's actually inside. Most likely the USB-interface is the same for both drives, and the mechanical enclosure is also the same, but the item with probably the highest failure-rate is the HDD inside... so this is surely comparing apples against oranges! For fun, see the review for the
500 GB version (0S03698) and notice (in the customer-feedback) how many drives listed there are actually the 1 TB version

In my opinion this is a VERY dishonest approach by Amazon, probably done in an attempt to make products look more popular/better selling than what they really are!
So, the good question: What HDD is actually inside, when you buy some external USB drive? Answer: No way to know in advance; can be this, can be that! Manufacturers of external HDD's probably use different HDD's (same size, same interface, same capacity, but different vendors), for cost and "security of supply" reasons. Example:
In the 1 TB Transcend Storejet 25H3P discussed in
this review, a Samsung/Seagate ST1000LM024 HDD is used. However, in another review covering exactly the same drive, the
Easycom review a Western Digital's Scorpio Blue WD10TPVT 1 TB drive is used! OK, so what if you love Samsung/Seagate and hate WD; get this 1 TB Transcend Storejet 25H3P, or not? Well, this boils down into being a pure luck of the draw; you buy what you buy, you get what you get!
A friend of mine has one of the 1 TB Transcend Storejet 25H3P's; the actual HDD inside is the Samsung/Seagate ST1000LM024 HN-M101MBB. Another friend of mine has the 2 TB version of the Transcend StoreJet 25H3P; the actual HDD inside this is a WD20NPVX which has received relatively poor feedback several places, so...
In the 1 TB Silicon Power A30 (that I have just received a few days ago), the actual HDD is a Samsung/Seagate ST1000LM024 HN-M101MBB. I haven't yet checked what HDD is inside the 2 TB Silicon A30 (that I have also just received a few days ago). The Samsung SpinPoint M8 ST1000LM024 has received somewhat mixed user-feedback various places (see e.g. on Newegg, Amazon etc.) while
this review was more positive, so I'm keeping my fingers crossed!
As mentioned above, I have been looking around quite a bit before purchasing the two Silicon Power A30 HDD’s mentioned, and no matter what HDD you look at (whether bought separate or in some USB-enclosure); no matter which HDD, you will find users that say: “My HDD was DOA” or “My HDD already failed after xx days/months”. So, really, and unfortunately, I don’t believe it is easy (or perhaps possible at all?) to find
the very best HDD from looking around this way; all manufacturers drives have some amount of failure rate, and users with failed drives will no doubt report back their negative experience much more often than happy customers will.
Most of us have probably had some negative experience with HDD’s over the time, so we probably all tend to keep this implicit in mind (saying to ourselves:
I’m surely *never* going to buy any WD drives again!! or:
No Seagate drives will never, ever again enter the doorstep to my house!! etc)… you see these type of bad-HDD-manufacturer statements often here in the forum, even by long-time members with many posts – and what it all boils down to (in my belief!) is simply… plain bad luck, provided of course, that the drive(s) have been used and handled as intended and not abused etc.
So, what can we do about bad luck? Keep more than one backup, and in the case of external drives try to omit the obvious weak points, which in my opinion is to get solid drives, and stay away from all that appear fragile or flimsy, such as the small type-B USB 3.0 connectors. If you wish to see the more mechanical robust type-A USB 3.0 connectors of the Silicon Power drives, then e.g. have a look in the following reviews:
Silicon Power Armor A30 1TB USB 3.0 Portable Hard Drive Review and
Silicon Power 1TB USB 3.0 “Shockproof” Portable Hard Drive Armor A30 Review and
Silicon Power Armor A30 1TB USB 3.0 External HDD Review and
Silicon Power Armor A30 2TB USB 3.0 Hard Drive - Featues and Inside Look
Note that my choice may, or may not, be good... I've only had both drives for a few days, and haven't used them very much yet. Final thing; you may want to get some sort of transport case for your external drive, if you wish/need to keep it even better protected during transport. I am very satisfied with the
Case Logic PHDC1 for large drives such as the Transcend Storejet 25H3P's and/or the Silicon Power A30's. For smaller external HDD's (e.g. like the HGST you mention), the
Case Logic QHDC-1 are perfectly suited.
NB: Beware that most external 2.5" HDD's are delivered formatted to FAT32 (which is directly usable on both Windows PC's and Mac's), but FAT32 will however only allow up to approx. 4.3 GB sized files. You may easily convert FAT32 to NTFS (the latter capable of holding much larger file-sizes than you will ever need!) with no loss of data; see e.g.
How to Convert FAT Disks to NTFS.
Good luck picking an extrenal 2.5" HDD and please let us know what you ended up buying, and your satisfaction?
PS: I altered the title of this thread slightly to be a little more (better!) descriptive... hope that's OK!
Johan