mdadm array disappearing disk device name changes

[Uchua]

I am running the arch on a raspberry pi as a low-power sftp/samba/cvs server for various purposes. I have two externally powered USB 2.0 hard drives hooked via a hub to the raspberry pi.

For the longest time the array had been working normally. Now after a few minutes to an hour the array disappears and /dev/sdb changes to /dev/sdc. I can easily rebuild the array by running mdadm --stop /dev/md0 and mdadm --assemble --scan and then again the array will just drop off and /dev/sdc becomes /dev/sdb again. I was thinking failing hardware at first but it doesn't seem like any of the data on the disk that is changing labels is corrupt. I tried looking up disks with randomly changing labels and haven't come upon anything useful. It also has random periods of extended stability then continues the behavior.

Any input on my problem would be greatly appreciated.

[WarheadsSE]

Check the power supply to the pi.

[Uchua]

The power supply for the pi seems to be fine. Using last doesn't show any reboot or shutdown that I haven't caused myself.

[dtruesdale]

I have found out from the Odroid forums that when delaing with drives you don't want to use /dev/sdax you want to use the UUID for the drive. That way if this happens when it comes back it re populates. You have a power issue. Best way to reoslve it is a 2A+ usb 4 port hub or power to each device individually. On my Pi I have a 2 TB external with it's own power supply. Same for the one hooked to my XU3.