Slower Disk speed when i added more drives? what can i do

[comet424]

so i bought a new norco 20 bay server case

my setup was

asus tuf x570 gaming board

lsi card 2 port

8 sata drives 7200 rpm and 1 nvme gen 3   and id get over 100mbs  and faster copying over network from ssd to nvme

 

but i upgraded to this case..  i had  15k sas had drives from a friend 300gb and 146gb

but now i get slower speeds i get 80mbs over the network  from ssD  to array and 80mbs from SSD to nvme... did  i configure somethjing wrong

the way i configure 20 bay case is

 

asus tuf x570 gaming

LSI card 2 port  ===> goes into a 4 port Expander card

4 mini sas cables to 16 ports

4 onboard sata cables to the remaining 4 ports on the case

 

i made 2 cache drives

2 146 gb drives   15km sas drives

6 300 gb drives  15km sas drives

i noticed every 2 drives is a parity or a mirror i guess as you dont get all the data

 

8  drives are array +nvme

and the last 4 sata drives  on the board  are set for unassigned drives

 

so i just practicing  as i wen from 8 drives to 20 

 

but i find its slow  80ms  i dont get the faster speeds i used to

 

did i configure something wrong?