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  #16  
Old January 30th 19, 07:10 AM posted to alt.comp.os.windows-10
Tim[_10_]
external usenet poster
 
Posts: 249
Default I need help!

Paul wrote in :

Tim wrote:
lonelydad wrote in
.28:

I have a WD Passbook 4tb USB drive.


So maybe the problem was with
insufficient power available. This would go along with the behavior
of the drive. I would keep showing up and then disappearing again.
Even when it didn't appear to the system, I could feel the heads
trying to load.


On 2.5" drives, they draw around 1000mA from the 500mA USB2 port.
This can cause the Polyfuse (rated at 1100mA) to open.

Polyfuses are polycrystalline. They become liquid phase when the
current flow is too high. When the overload is removed and they cool
off, the material hardens back into a crystal.

It's better if an external hard drive is powered by an
external source, but they don't always put a barrel
connector on the external drive casing.

Just one of those "electrical disaster areas" some
group of people thought was a fine idea.

Once the drive is spinning, power demand drops, sometimes
even below the 500mA level. The drive can then continue
spinning. But for drives with "parking habits", they will
stop, then start moments later, applying the "trial by fire"
to the Polyfuse again.


Paul

First, I wasn't clear. Theses were USB3 ports, if that makes a
difference.
Second, I realized reading your response that this drive does indeed have
a separate power supply, so so much for that theory.

I guess I am just thankful it cleared itself up so I got my data back.
More backups! More backups! More backups! I just wish there was some sort
of tape drive that was reasonably priced that would hold a terrabyte or
two. Back in the day we used TK70s to back up our NT server, but that was
when drives were measured in tens of gigabytes, not terabytes.
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  #17  
Old January 30th 19, 07:46 AM posted to alt.comp.os.windows-10
Paul[_32_]
external usenet poster
 
Posts: 11,873
Default I need help!

Tim wrote:
Paul wrote in :

Tim wrote:
lonelydad wrote in
.28:

I have a WD Passbook 4tb USB drive.
So maybe the problem was with
insufficient power available. This would go along with the behavior
of the drive. I would keep showing up and then disappearing again.
Even when it didn't appear to the system, I could feel the heads
trying to load.

On 2.5" drives, they draw around 1000mA from the 500mA USB2 port.
This can cause the Polyfuse (rated at 1100mA) to open.

Polyfuses are polycrystalline. They become liquid phase when the
current flow is too high. When the overload is removed and they cool
off, the material hardens back into a crystal.

It's better if an external hard drive is powered by an
external source, but they don't always put a barrel
connector on the external drive casing.

Just one of those "electrical disaster areas" some
group of people thought was a fine idea.

Once the drive is spinning, power demand drops, sometimes
even below the 500mA level. The drive can then continue
spinning. But for drives with "parking habits", they will
stop, then start moments later, applying the "trial by fire"
to the Polyfuse again.


Paul

First, I wasn't clear. Theses were USB3 ports, if that makes a
difference.
Second, I realized reading your response that this drive does indeed have
a separate power supply, so so much for that theory.

I guess I am just thankful it cleared itself up so I got my data back.
More backups! More backups! More backups! I just wish there was some sort
of tape drive that was reasonably priced that would hold a terrabyte or
two. Back in the day we used TK70s to back up our NT server, but that was
when drives were measured in tens of gigabytes, not terabytes.


Well, that's excellent news, that you have some good
kit there for the job. And now your focus can switch
to looking at the drive health (SMART). You might still
have to pull the drive from the enclosure, and put it
on a SATA port, to check it out.

I think things like SeaTools will test drives in Seagate-made
enclosures. It's possible the WDC software does the same
for their drive products. Perhaps they have access to the
SMART info. In some cases, the tool is actually using the
SMART short test or the SMART long test, rather than
crafting a custom test for the purpose. So that's a way to
get an opinion about a drive.

Not every ATA/ATAPI feature has an equivalent via USB
mass storage. Sometimes a "passthru" scheme is needed to
pass commands through to the device and get hardware
level feedback. I'd have to run off and research how
that works on USB, to say more about it. As an example, it's
pretty hard to get SMART info when RAID is being used.
There are bound to be other cases where SMART is
also hidden.

Paul
  #18  
Old January 30th 19, 11:22 AM posted to alt.comp.os.windows-10
Andy Burns[_6_]
external usenet poster
 
Posts: 1,318
Default I need help!

Paul wrote:

It's better if an external hard drive is powered by an
external source, but they don't always put a barrel
connector on the external drive casing.


They do often come with a USB 'Y' cable to split the load across two USB
ports though.
  #19  
Old January 30th 19, 12:48 PM posted to alt.comp.os.windows-10
Paul[_32_]
external usenet poster
 
Posts: 11,873
Default I need help!

Andy Burns wrote:
Paul wrote:

It's better if an external hard drive is powered by an
external source, but they don't always put a barrel
connector on the external drive casing.


They do often come with a USB 'Y' cable to split the load across two USB
ports though.


At one time, it was popular to put the Y or Hydra cable in the box.

It's less common today.

You can see a number of possibilities actually.

1) External 2.5" drive with just a USB

2) External 2.5" drive with a USB plus a barrel power input.

Then cables:

1) Regular cable, with the possibility of the Polyfuse opening.

2) The Y-cable, with four pins on one USB connector and two
pins (VCC/GND) on the other USB connector.

3) Two cables. A regular USB cable with four pins (data).
A second USB cable with a barrel on the other end (power).
The second cable only has VCC and GND on the USB end.
It's effectively a variant of the Y-cable, but done as
two cables.

*******

A motherboard or adapter card with USB3, may have a larger
fuse value associated with the port. Which will help with
the Polyfuse opening issue. Even if the external drive standard
is only USB2 and runs at 30MB/sec, the usage of the USB3 port
could help with the powering issue.

USB2 Standard loads 100mA or 500mA (encoded in config info)
Fuse set at 1100mA (desktop)
Electronic Fuse set to as low as 500ma (laptop) === (design mistake)

USB3 Standard load now includes 900mA (how encoded ? dunno)
Fuse set at 2000mA (desktop) === as seen on the USB3.1
card I just checked
Presumably a newer "policeman chip" exists for laptop

By using a USB3 port with your external 2.5" drive, the
fuse should not open. Even under stall conditions,
hard drive motors have a current limiting scheme
(there is a three phase motor controller with quite complex
capabilities and low torque ripple). On 2.5" drives, they
generally aim for a 5V at 1 amp limit (twice the USB2 spec).

The hard drive designer simply sets the motor current to some
value, where "more current = ready sooner". Internal
boot drives receive a higher setting than internal
archive/backup sized drives. A 4TB drive spins up
slower than a 500GB boot drive, not necessarily just
because of the mass involved, but also because the
motor current limit is different. I could see this
by measuring some 3.5" ones.

The 2.5" drives come in 1 or 2 platters for "regular" drives,
and up to 5 platters for the 15mm drives used in external
WDC or Seagate 2.5" drive products. The 15mm drives
used for archival storage at the 2.5" design point,
don't fit laptop bays, and the drives are not for
sale at retail. (The ones on Ebay are shucked from
casings and sold as raw mechanisms. The manufacturer
doesn't like this, and found a clever way to put a
stop to it.)

Paul


 




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