Mechanical- sounds like an excuse to me. Technically virtually anything (and nothing) can cause a drive to fail but I'd certainly want to know if my application was going to kill the hardware it was running on if it was put under load. Id be discussing this with the client along with their choice of hardware if it poses a risk to their application.
Solid Sate - Potentially some merit to what they're say if the concern is about shortening lifespan (wearleveling etc) of the drive for what they might consider unnecessary testing. Again, another chat with the client about hardware suitability and scalability.
I'd be asking the operations contractor some more detailed questions about exactly their concern is and what their plan is to mitigate those failures in a real world scenario.
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Data Recovery Services in the UK.
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