Question Data transfer freezes and resumes on my rackmount server.

Jan 10, 2021
Hey everyone,
I have a HP Proliant DL380 G5 that I got for quite cheap on eBay, and the thing still works like a charm. I am running Windows Server 2012 R2, and have a WD Blue 500GB SATA HDD as the boot disk, 3 Seagate Barracuda 1TB Drives combined in a RAID 0 as a logical drive, and 4 HGST 500GB SAS HDDs in RAID 0 as a logical drive. The server was working quite well before I introduced the HGST SAS drives into the controller array. Transfer speeds were good, and boot times were fast. Now, after installing the SAS drives, only the SAS drives work. And I mean they work insanely well, data transfers are crazy fast. But I cannot say the same for the 3 Barracuda drives. When I attempt to transfer files from anywhere (Internet, Local Network, Local HDD transfers) it goes REAAAALLY fast for about 2 seconds, like about 700MB/s (Yes megabytes not bits) then it completely drops, and then continue at about 2 MB/s and then continues to start and stop until the transfer is finished. i feel like some sort of memory cache is filling up rapidly, but the drives are not writing properly. Here is what I have tried so far:
- Individually removed each SATA drive and cleaned them in DiskPart
-Changed drive bays
-Changed logical drive type so that they are all individual logical drives.
-Changed RAID type.

The storage controller is an HP P400. I am wondering if the SAS drives to put the controller into SAS mode or something like that, and it is not agreeing with the SATA drives. it doesn't make sense because the boot disk is SATA, and had good read speeds, and the write speeds are alright, as to be expected from a slim 2.5" HDD. Any pointers as to what could be causing this? I am migrating all of my data off the HGST disks onto an external drive array so I can edit these drives as I please. After the transfer, I am going to try running the system without the SAS drives installed. I will update this thread accordingly.