Why USB powered drive only?

I’ve read and heard numerous times from Tablo that the HDD should/must be USB powered, yet I have read several posts about people using external powered drives. I myself am using a Cavalry 1TB external powered drive, and all seems to be well, although I’ve just started using the Tablo for the first time during this past week. Obviously an externally powered drive will work, but I’m wondering what kind of issues can be traced to this configuration.

None. I use an internal HDD with a HDD enclosure that has a fan for cooling and that is externally powered. See below:


With the new firmware coming up this week (hopefully), users should be fine with either USB powered or plug in drives. Due to compatibility issues early on, the USB powered drives were more successful with the Tablo than the others, which is why they were recommended. After this update, hopefully every drive will work.

The 5 TB drive that they tested in house is externally powered and they say it works without any flaws. As you might have seen elsewhere, I have not swapped drives yet.

Honestly I don’t see why it wasn’t released already, and list the drives they are having problems with. They most likely don’t want to risk deals with the manufactures. @TabloSupport are all the remaining problem drives from the same manufacture? Seagate was nice to give you a 5 TB to test the beta version of the firmware with. You can release the firmware now, and say the Seagate drive that you have tested without any problems. Of course that would be giving preference to one disk manufacture. Next time, perhaps more disk manufactures will be willing to let you test their model, so you will endorse it :slight_smile:

So it’s sounding like an earlier problem that’s gradually being phased out with firmware updates, and as long as it works at all there should be no problems with it?

Thanks, all.

As I understand it, Tablo has tested specific drives and those are the ones they recommend. Other drives may or may not work. Way back when I was a very green engineer just starting out, I had a manager who’s philosophy was “If it hasn’t been tested, it doesn’t work.” Later in my career, I used that phrase many times on young engineers who were working for me, as it’s a very good philosophy that served me well over the years. Fact of the matter is, if Tablo hasn’t verified that a specific drive works with their products, and if you want to use it, you do so at your own risk. It may not work at all, or it may work unreliably.

You can think of the USB interface as being comprised of two parts, power and data. Not all USB interfaces or cables carry both, though they usually do. In some cases, a peripheral device with a USB interface may consume more power than a typical USB interface can provide, so it carries it’s own power supply separate and distinct from any power that might be provided over the USB interface. In Tablo’s case, it’s really the data portion of the USB interface that’s important, as it appears to have sufficient capability to power most external drives. There are a set of communications protocols that take place between the USB drive and the Tablo (or other device, such as a laptop) that are used to perform certain functions such as read, write, erase, etc. In order for the Tablo and USB drive to properly interoperate, they USB drive and Tablo must be able to speak the same language, i.e. the USB drive must understand the commands sent to it from the Tablo, and Tablo must understand the information coming back from the USB drive. Also, the external drive must respond quickly enough or information send back to the Tablo may be missed, or the drive may not be able to keep up with how quickly Tablo is sending it data, such as a program you want to record. Now the communications protocols and timing are pretty standard, and if PROPERLY IMPLEMENTED by the manufacturer, should work, but going back to the philosophy I noted earlier, you have to test it to make sure. Companies usually devote separate departments entirely devoted to interoperability testing for this reason. And I’m sure in Tablo’s case, that they only recommend external USB drives that they’ve tested and therefor know for a fact that they work with their products.

For those that want to get the first drive tested it is http://www.amazon.com/Seagate-Expansion-Desktop-External-STBV5000100/dp/B00JT0EGPW

Newegg also carries it. You might want to check Newegg ebay as that is where I got mine and it was cheaper than Newegg.com. Also note that there is a newer model of the drive. The newer model has NOT been tested, so I suggest getting this model.

The reason why we warned against externally powered drives was because many of them have 4K sector sizes which the current firmware doesn’t support.