I'm having this same issue as well. While moving anything to the disk array (IE with the mover) trying to read from the array is a futile effort as it slows down to an unusable degree. Reverted to 6.6.7 and things seem to work much better, with the array usable again while the mover is running.
[6.7.x] Very slow array concurrent performance
in Stable Releases
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I'm having this same issue as well. While moving anything to the disk array (IE with the mover) trying to read from the array is a futile effort as it slows down to an unusable degree. Reverted to 6.6.7 and things seem to work much better, with the array usable again while the mover is running.