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External Backup?



 
 
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  #11  
Old July 6th 19, 04:59 AM posted to alt.comp.hardware
Paul[_28_]
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Posts: 1,112
Default External Backup?

~misfit~ wrote:
On 6/07/2019 10:34 AM, VanguardLH wrote:


The OP said he *thinks* an A/C powered USB enclosure *might* be more
reliable than using a USB port. His experience has been the A/C powered
USB drives were more reliable than the port-powered USB drives. My
experience has been the port-powered USB drives work just fine for a
long time -- PROVIDED you use a port that supplies enough power (USB3)
or you know the HDD inside the enclosure can work on just one USB2 port
instead of requiring 2 USB2 ports via Y-adapter. I've had USB2 HDDs,
too, and those required the Y-adapter, and as long as I used it to get
power from 2 USB2 ports then the USB HDD worked just fine. With just
one USB2 port, those old USB2 HDDs might not spin up.


A problem with those USB2 'Y' adapter things is sometimes you need to be
sure to plug in the USB A plug with the data pins *after* the auxiliary
power supply USB A plug. (Or plug them both in at the same time.)

I had a drive corrupt itself because of plugging them in in the wrong
order once (a few years ago now though).


The situation is entirely unsatisfactory.

Period and end of story.

Do customers need an engineering degree to use a product ?

*******

I have no "Slim this" or "Passport that" here.

Can you guess why ???

Who wants to play whack-a-mole with storage devices.

Especially the 2.5" ones with the *captive* USB
ports, so you don't even have a SATA port to use.
You can't even shuck those and work on them via
a properly powered SATA port.

Paul

  #12  
Old July 6th 19, 05:48 AM posted to alt.comp.hardware
VanguardLH[_2_]
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Posts: 1,350
Default External Backup?

misfit wrote:

A problem with those USB2 'Y' adapter things is sometimes you need to
be sure to plug in the USB A plug with the data pins *after* the
auxiliary power supply USB A plug. (Or plug them both in at the same
time.)

I had a drive corrupt itself because of plugging them in in the wrong
order once (a few years ago now though).


I always plugged in the computer-side USB connectors to the PC/laptop
USB ports. That way, with one as power only (just the +5V and GND
lines) and the other as power+data (+5V, GND, Data+, Data-), there was
yet no device added, and the PC/laptop's USB ports where not both trying
to connect the data lines to each other. I plugged in last the USB
drive.

Plugging in the USB drive first to the Y-adapter might have problems if
you already have the cable plugged into the USB device. After
connecting to the USB device and you first plug in the pwr+data end, it
may not have enough power to spin up the drive or operation is flaky.
Power is insufficient. If you first plugged in the pwr-only end, the
drive might not spin up, and then plugging in the other end (with pwr
and data) means trying spin up the drive while it tries trying to send
its presentation data during the handshaking. You'd think the drive
would wait until it has ample power, but maybe it thinks it does with
just the pwr-only connection. Neither way was reliable.

Plugging in the computer-end of the Y-adapter does nothing by itself.
Plugging in the USB drive last makes sure both the initial power was
sufficient and the data lines (from only 1 USB port) were ready. USB
connectors are designed to plug in the power lines first (and disconnect
last), and the data lines connect after the pwr lines on plug in and
disconnect first on pull out.

https://upload.wikimedia.org/wikiped...px-USB.svg.png

The data pins are shorter. The longer power pins connect first on plug
in, and disconnect last on pull out. Power is supposed to be ready
before connecting the data lines, and power must be sufficient before
data signalling begins. I don't what is the expected or minimal lead
time to present power before the data lines connect. It's like very
short, like milliseconds, due to the very small difference in the length
of the pwr and data pins (which is present in both male and female
connectors, so the length difference is doubled).

I don't know that I ever read or even had instructions on how to use the
Y-adapter cables that came with the USB2 HDDs that needed them. Just
seemed the proper order: plug the computer ends in first, then plug into
the USB device.

I always disliked having to use a Y-adapter. I had to make sure to tote
it along with the USB HDD. I had to pause before plugging in to make
sure I got the connect order correct. I was glad when drives required
less startup or surge power, so only 1 computer-side USB port was
needed.

Power available at the USB port (power source side aka downstream port):
USB1.x: 0.5A, 2.5W, 5 unit loads (1 unit load = 0.1A)
USB2.x: 0.5A, 2.5W, 5 unit loads (1 unit load = 0.1A)
USB3.0: 0.9A, 4.5W, 6 unit loads (1 unit load = 0.15A)
USB3.2gen2: 1.5A, 7.5W, 6 unit loads (1 unit load = 0.25A)
USB-C : 1.5A, 7.5W, or 3A, 15W (aka Thunderbolt)

Alas, drive specs rarely quote the minimal current needed to spin up.
They may not even rate themself regarding unit load(s). I remember USB
HDDs that didn't supply a Y-adapter but they were marginal (at the max
load) of a USB port, so many users considered them unreliable. Using a
Y-adapter fixed that problem. Don't remember the data corruption you
mentioned with a Y-adapter, but maybe that can happen when not using the
proper connection order.

The OP seems determined to get newer USB HDDs that have their own AC
power adapter, so the only connection the drive really needs to the
source are the differential data lines. However, while I disliked
having to tote around a Y-adapter, I can't see toting around some power
adapter as being more portable. Those USB HDDs that I've had with a
power adapter were pretty much stationery, not toted around. At that
point, forget getting a portable USB HDD and just get the big fat USB
HDDs that are designed to sit (usually upright) on the desk next to the
desktop PC.
 




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