After some consultation with members of the GT IT community (thank you specifically, Didier Contis for raising the awareness of the issue), as well as our vendor, we have identified the cause of the high rate of disk failures plaguing storage units purchased a little bit more than a year ago.
An update to the firmwares running on the internal backplanes of the storage arrays was necessary, and performance and availability were greatly improved immediately after these were applied on the arrays. These firmwares are normally manufacturer maintained materials only, and aren’t readily available to the public like controller firmwares are, which led to some additional delays before repairs.
That said, we have retained the firmwares and the software used to apply them for any future use should other units have issues.