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The SSD part of the Momentus XT is hidden from the uses and you have no access to it. The SSD part should be aligned before it leaves the factory.
The HDD part you can of course access, but alignment on an HDD should not have any noticeable difference in its performance on this class of HDD.
If you want to align the HDD part, you can follow the instructions on "partition alignment" in the SSD FAQ here.
You have to delete the partition first which means all data is gone.