What are the differences between the blow backplane models?
BPN-SAS-826-7EL1 1 BPN-SAS-826-7-EL1 for SC847 Chassis
BPN-SAS-826EL1 1 2U SAS / SATA Expander Backplane with single LSI SASX28 Expander Chip
Can I put the first one into a SC826 Chassis?
No. BPN-SAS-846-7EL1 is for the HDDs in rear side of 847 chassis.
The design is different from those for 826.