The following messages are in the system log very often:

Mar 20 18:00:56 aidas-gsi smartd[1076]: Device: /dev/sdd [SAT], 2224 Currently unreadable (pending) sectors
Mar 20 18:00:56 aidas-gsi smartd[1076]: Device: /dev/sdd [SAT], 257 Offline uncorrectable sectors

This (to me) suggests /dev/sdd may be failing. It should be backed up and later replaced (it is not used at the moment for /TapeData, older disk)