Poor r/rw speeds - Dell R3x0

Hi All

I am hoping someone can point me in the right direction.

I have a Dell R310 ( Same issue on a R320 ) with a PERC H700 Controller that has 4x Samsung 850 EVO 500GB SSD's attached to it, these were initially configured in a raid 10 array and then Ubuntu installed to which I was getting great read and write speeds for the first few days, there after the r/rw is down to 25Mb/s

I then scrapped that idea and set up the 4 disks each in their own RAID 0 ( no read ahead, with write through and size = 128k ) and tried to use mdadm raid 10 through ubuntu. Same results. Incredible speeds for the first few days and now its back down to 25Mb/s

Any suggestions on what I can do to get better speeds? Is there some part of the recipe I am missing

PERC Versions

Package:12.10.7-0001

FW Version:2.100.03-4651

BIOS Version 3.18.00

Any help is appreciated, thank you!