I purchased a Dell EMC R740 with 8 Intel S3520 SATA 6 Gbps SSD drives. The problem I have is that no matter what RAID configuration I select I seem to be limited to roughly 5 Gbps. I would think that 8 drives in a raid 5 configuration would operate at 6 Gbps x 8 = 48 Gbps. I can understand a little loss for parity bit calculations but I should be seeing better performance. The controller card is rated for 12 Gbps so I would expect to see that speed at a minimum. We have tried various RAID modes and settings on the controller with no luck.
We also purchased 8 Seagate Nytro 3730 SAS 12 Gbps SSD cards and put them in the server with the exact same results.
We have spend hours on the phone with Dell and they said that the SSDs are rated at 6 Gbps and that is all they will do no matter the RAID configuration. When we told Dell we purchased new drives rated at 12 Gbps and they were not working either they said there is code in the controller to keep it from performing with non-Dell drives.
Am I correct on my raid/speed thoughts? Is there a different controller that will perform better? Any other ideas?