Software caused connection abort

I've got an external ssd that was giving me Transport endpoint is not connected errors after a few hours of a lengthy rsync I was doing. So I set the 'advanced power options' to never power-off : jeremy@jeremy-Blade:~$jeremy@jeremy-Blade:~$ sudo hdparm -B 0 /dev/sg0 [sudo] password for jeremy: /dev/sg0: setting Advanced Power Management level to 0x00 (0) SG_IO: bad/missing sense data, sb[]: 70 00 05 00 00 00 00 0a 00 00 00 00 20 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 SG_IO: bad/missing sense data, sb[]: 70 00 05 00 00 00 00 0a 00 00 00 00 20 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 APM_level = not supported which as far as I can tell fixed that problem (at least the rsync completed subsequently, despite the 'APM_level = not supported' caveat). However when I run some checks to see if the rsync was largely successful, I hit 'software caused connection abort' and then the transport endpoint err again, with disk no longer mounted: jeremy@jeremy-Blade:~$ find /media/jeremy/JR_SSD/tms/ -type f |wc -l find: ‘/media/jeremy/JR_SSD/tms/20140221/images’: Software caused connection abort find: ‘/media/jeremy/JR_SSD/tms/20140222’: Transport endpoint is not connected .... So my question is what's gone wrong, and/or how to avoid this 'software caused connected abort' business. None of the other SO threads on this err seem relevant. There should be around 30 million files found by the find, taking 350Gb, if that makes any difference. edit df -T lists the ssd as type:fuseblk, internal hd is type:ext4