Tuesday, February 2, 2016

Intermittent Drop Out - USB, Thunderbolt, FireWire and more...

If you are like me - a poor guy with very little money in the bank, most likely you would buy a cheap enclosure and pop in your own hard disk or SSD. I did that all the time until someday I learned it is not saving me any money, it probably costs more of my time to find out the problem.

Have you ever removed the hard disk from a portable drive, such as Seagate's, and replace it with your own SSD? this can definitely give you a fairly fast speed, however, you should not do this. Read the technology specification FIRST! and pay attention on the power budget.

USB 3.0 can provide 900mA/5V, so total is 4.5W per port. If you read the 1TB SSD's manufacturer website, you may find that they require way more than 4.5W, sometimes, it's 7W or more. The same requirement applied to portable hard disk too.

Tell me how could you make a USB 3.0 portable enclosure which only draw 4.5W from the host to support 7W to the SSD?

You may said: Wait a second, but, it works for me, I could see the SSD in my system, I could use it, I could format it, erase the data, the only problem is it could drop out intermittently.

Well, read the SSD's data sheet again, did you see "Peak power consumption", "Average power consumption" and such? and what is the capacity of your SSD? most 256 GB or below might be OK, the 500GB and 1TB are very power hungry ones, you should not rely on 4.5W bus power.

What happened when SSD does not get enough power? You probably know the answer - Disconnected or Dropout or System hang. Data would be lost for sure. This can explain why you see "Intermittent Drop Out" if you plan to use your own SSD in portable device.

So what is the solution? Use the power adapter to the enclosure! YES and that is the ONLY answer.

Aside the enclosure power budget problem, I have seen many people using Samsung T3 Portable SSD - 500GB - USB 3.1 External SSD (MU-PT500B/AM) and plug it in to one of the following Hubs

Anker Ultra Slim 4-Port USB 3.0 Data Hub
USB C Hub, HooToo Shuttle 3.1 Type C Hub with Power Delivery for Charging, HDMI Output, Card Reader, 3 USB 3.0 Ports - Silver
AUKEY USB C Hub, 4-Port USB 3.0, Aluminum Body for MacBook, Google Chromebook Pixel

Satechi Type-C USB 3.0 3 in 1 Combo Hub for MacBook 12-Inch (with USB -C Charging Port) (Space Gray)

In my opinion, this would not work. These bus powered USB hubs are all failed from the design phase. You should not do bus powered hub that has more than 1 USB 3.0 port. Apple's laptop does not provide too much power to drive a bus powered hub that has 2 or more than 2 USB 3 ports. If you have a hub, does not matter it's USB 3 or USB 3.1, you need an external power to the hub. For those hubs that can do both bus powered and self powered should tell customers only use self powered mode. This can prevent customers from data lost and unstable system.

If you have MacBook 2015, and want to add an external USB hub or dock, your best bet is OWC USB-C dock or CalDigit USB-C dock, or any hub that does have correct power budget for all the extended ports plus the system itself. You do not want to buy a hub that can only rely on the power from Mac or PC laptops, and you do not want to buy a dock that came with a 72W power supply and claim can provide 7.5W on 5 of the USB 3.0 ports while providing 30W to charge MacBook. This does not make sense to me. Do the MATH yourself! ;)

Update 9/9/16: I am using CalDigit USB-C dock now, it works great and has correct power budget and buffer for the entire system and ports. No dropout bus powered drive.



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