Linux on PPC64 use 64kB page size, making this crash whereas it works well.
https://github.com/mongodb/mongo/pull/735
SERVER-13452 Add PPC64 as a supported platform
I/O Limits: block sizes, alignment and I/O hints
PowerLinux Community - Implementing MongoDB on IBM Power Systems
Pull Request #735
Pull Request #766
Pull Request #769
Quora: Why does O_DIRECT require I/O to be 512-byte aligned?