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#16
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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
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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
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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
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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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