This question refers specifically to the use of external 2.5" drives, spinning or SSD.
External drives on USB hubs we all know are very flaky, even for powered hubs.
It was surprising that I couldn't find an existing answer to this question. Quoting experience is one thing, but a technical reason why USB hubs are unreliable and why Thunderbolt is better (if it indeed is for this use case) would be excellent.
It's a Thunderbolt 2 dock I'd be looking to get, for a 2015 MBP, if that helps.
I have a similar question, in trying to pick between different backup options. I saw the following on this OWC blog post - down in the comment section, where the author, an engineer/software developer at OWC, says:
APFS only protects the file system information from data corruption (e.g. the file name, size, modification date, etc.). It offers no protection to the actual file data itself.
This only means that an APFS volume is less likely to become unmountable. It does not mean that your file is less likely to be corrupted.
If your disk is in a USB enclosure (USB 3 or USB-C, formally known as USB 3.1 Gen 2), then the I would switch to a Thunderbolt enclosure. We routinely see more problems with USB enclosures.
The author further explained by saying:
I would switch from USB to Thunderbolt if it were me (and both of my personal enclosures are ThunderBay 4s). I know they are more expense but they are definitely worth the money. There is a certain type of volume corruption which we occasionally see, but we only ever see it on USB enclosures. I don’t believe this data corruption is limited to SoftRAID volumes.
I have never felt like USB storage software is a priority at Apple. We have reported numerous bugs to them and most of the time we get back a response which indicates that they are not willing to address the problem.
And lastly:
Only you know how important your data is to you. If it were me, I would Thunderbolt storage for at least one of your backups. In our office, we have 4 copies of all important files. The onsite backups are all on Thunderbolt storage (RAID 1+0) and the offsite ones are on USB-C. I don’t use USB 3.0 for single drives or RAID volumes and don’t use USB-C for RAID volumes. USB-C seems to be okay when only a single disk is involved.
This is just based on my experience. Your experience might be different.
Although his discussion relates to the choice of hard drive enclosures rather than external hubs, the reasons behind such flakiness might be pertinent to hubs as well.
External drives on USB hubs we all know are very flaky, even for powered hubs.
This is not exactly accurate. The reliability of USB Hubs/drives (any product for that matter) is directly related to the quality of the product. Speaking from personal experience, I have found when I purchase from reputable brands, I rarely have issues. Anecdotally, I still have an old USB 1.1, 3.5” HDD (must be about 20 years old now) with external power supply that still works. It serves as an archival drive for an old Dell desktop running FreeBSD. The drive has been replaced twice. The USB to IDE controller board works with zero issues.
Personally, I rarely use bus powered hubs (they get their power from the USB port). I prefer to use powered hubs because they have the ability to provide a steady consistent stream of current. Typically, the USB bus can handle up to 5 devices at 100mA or 500mA total (USB 2.0).
500mA is typically enough for a 3.5” drive, but if it isn’t efficient (cheap components) it can easily overwhelm that, especially if you have other USB peripherals attached. I prefer to ensure there is adequate power with a powered hub and an externally powered drive.
…a technical reason why USB hubs are unreliable and why Thunderbolt is better (if it indeed is for this use case) would be excellent.
Not to belabor the point, but you’ll see unreliability in any product where the product strategy is based on being the cost leader. A discount hub for $15 costs the distributor $7.50 and the manufacturer $1.50 for parts and labor. Their goal is to maximize profitability and that means the cheapest (Chineseium) components they can source.
A reputable brand that takes a more pragmatic approach to gaining market share will user better components, better manufacturing and labor thus leading to higher prices.
So, is USB unreliable whereas Thunderbolt is inherently so? No.
Thunderbolt licensing was prohibitively expensive. The technology is more complex than USB and is thusly, more expensive. The Thunderbolt controller chips are only made by a handful of fabs so, that too contributes to the cost (supply and demand).
USB is ubiquitous and doesn't require certification to work or sell the product thus, is quite easy to flood the market with products. Almost any fab can churn out USB controllers for next to nothing.
What unfortunately happens is the comparison of bargain basement USB up against mid to top-tier Thunderbolt products. It’s not an apples-to-apples comparison by any stretch. If you compare products of the same quality level, you’ll find that USB holds it own.
It's a Thunderbolt 2 dock I'd be looking to get, for a 2015 MBP, if that helps.
Get the Thunderbolt dock because it offers a greater range of expandability. Remember it’s DisplayPort, PCIe, and USB on a single cable that is capable of daisy chaining peripherals.
If you don’t need that level of performance, USB is fine. Just be sure to put quality as a priority when selecting a unit.
