Posts: 40
Joined: Wed Mar 14, 2018 10:50 pm
Location: Finland

SSD randomly disconnecting when moving my 3B

Mon Aug 19, 2019 2:10 am

I have a problem, on 3B, of external USB disk (an SSD) that I use as a root filesystem, randomly disconnecting if I move the Pi around or change its position or orientation on my table. It's located under a display at the moment.

I've been unable to really figure out whether the problem is with the power connector or the USB connector to the disk. I have tried changing cables, but I noticed that the combined power requirement of the Pi and the disk is such that a normal micro-USB cable will not do and I see the lightning symbol all the time. I have two premium micro-USB cables. Neither show the lightning symbol, even if I stress test both CPU and disk. But they are quite stiff. Which made me suspect that the normal, more flexible cable would not cause those disconnects.

The cable from the Pi to the disk is a short one. So it should not cause a voltage drop. But when the disconnect happens, the Pi never reboots. It just kind of "loses" the root disk, and the only way forward is to reset it.

I wonder if any, some or many have experienced something like this. I will keep on shuffling all my cables to see what is it really about.

Posts: 5601
Joined: Thu May 05, 2016 9:33 am
Location: Paris, France

Re: SSD randomly disconnecting when moving my 3B

Mon Aug 19, 2019 10:26 am

If the root filesystem drops the system freezes or crashes. It’s not recoverable.
A plug might be a bit loose.
"S'il n'y a pas de solution, c'est qu'il n'y a pas de problème." Les Shadoks, J. Rouxel

Posts: 920
Joined: Mon May 20, 2019 11:28 pm
Location: The Frozen North (AKA Canada)

Re: SSD randomly disconnecting when moving my 3B

Mon Aug 19, 2019 11:46 am

Is the SSD in an enclosure or just plugged into a USB-SATA interface cable? Some enclosures do not promote a particularly solid connection and the SSD-interface connection might be the issue. I know my enclosure as shipped, relies on a small bit of foam to keep the SSD connected (I guess to account for size variation in SSD case molding.

You also could have a USB cable that has some issues. If flexing the cable causes the issue I would look at the cable. This is super common in cheap micro USB charging cables and bad lighting cables. Pay particular attention to right after the molding and strain relief at the ends.

Also, do you have a "real" power supply for the Pi? I have had the 128 Gb SSD connected to a 3B+ and a 4B (both with "official" power supplies) and have never had any connectivity issue, or even seen the lightning symbol.

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