Add SSD to RN528X

Thank you for the nice photos of the RN528X motherboard! 
I see now how it differs from the 6-bay RN526X - the PCI-style connectors for the HDD backplane are longer, allowing for more SATA lanes.

I'm still curious though, what controller is used for the 2 extra disks? The D-1508 has only 6 built-in SATA channels. And the extra Marvel 88SE9170 chip on the motherboard (at least that's what my RN526X has) provides only 2 extra SATA channels - one for the M.2 and one for the eSATA connector on the back.

Is it possible that the 8-disk RN528X has a different Marvel chip? Can you post the output of 

lspci|grep SATA

Also, it might be instructive to see the output of `lsscsi`. Here's for example mine, with 5 bays occupied with 4TB WDs, an M.2 SSD in the slot on the back, and an external Seagate USB-enclosure:

root@RN526X:~# lsscsi
[0:0:0:0]    disk    ATA      WDC WD4000FYYZ-0 1K03  /dev/sda 
[1:0:0:0]    disk    ATA      WDC WD4000FYYZ-0 1K03  /dev/sdb 
[2:0:0:0]    disk    ATA      WDC WD4000FYYZ-0 1K03  /dev/sdc 
[3:0:0:0]    disk    ATA      WDC WD4000FYYZ-0 1K03  /dev/sdd 
[4:0:0:0]    disk    ATA      WDC WD4000FYYZ-0 1K03  /dev/sde 
[10:0:0:0]   disk    ATA      TS128GMTS400SE2  5L5   /dev/sdf 
[13:0:0:0]   disk    Seagate  Backup+ Hub BK   D781  /dev/sdg