PowerEdge T620 very slow disk performance

Hello,

We have a T620 with a H710p controller with battery backup (battery in good shape) running win2012 R2 with all the latest updates.   We applied an SUU a few months ago and since then it has been VERY slow.  We have over 2TB free.

When we create a VHDX file the server is basically unusable while it does this.   Also it slows down when copying to another server.

We've tried:

Uninstalling all antivirus and rebooting.

Cold Booting

Defragging the disk

Testing creating a VHDX on another partition.

Changing to every possible cache policy including disabling it.

We've downloaded the latest SUU again   The only option upgrading to the same firmware.

Downloading the RAID firmware indivudually

Downloading the latest RAID drivers individually.

Anyone have any suggestions?   I'm a bit uncomfortable downgrading the firmware only because I've never done it before.