hard drive - SSD/HDD not exceeding 120 MB/s

SO here is the situation: First this was my old PC, it had a 2x 1TB RAID 0 and a Corsair Force 3 SSD in it. This were the old speeds, measured by HDTune Pro.

2x 1TB RAID 0:

Corsair Force 3 SSD

Then my dad got my PC and we had several issues, in the end turned out both RAID and SSD controller were malfunctioning causing BlueScreens on 100% load. Removed the RAID 0, but leaving the HDD's intact and bought an Samsung 840 EVO 120GB, though the Corsair SSD is still in the system, just not as sytem disk anymore.

1TB HDD (one of them):

Corsair SSD:

Samsung SSD:

We did not assemble the PC ourselves, so answering some technical questions might be more difficult, though we will do our best.

First thing we noticed is that the Samsung 840 EVO is no where reaching it's advertised speed, even an Samsung 840 250GB (non-EVO) is reaching 350 MB/s in my own PC.

Then we noticed that both SSD's are capped at 120 MB/s exactly, not sure if this is being caused by HDTune Pro, but very unlikely. And even worse, the Corsair Forza 3 was running faster before the system got reassembled.

Does anyone have any clue what is going on?

Answer

The potential causes can vary widely so please consider the following:

• Your speeds are actually correct for both HDD and SSD if your motherboard is using SATA1 ports


• IDE mode vs AHCI will also cause a considerable speed difference even on the same exact SATA version for both HDD and more noticeably on SSD


• SSD companies have been known to benchmark using default settings with ATTO Disk Benchmark so that is what I use as well


• If an SSD is more than about 50% full then benchmarks will suffer


• If an SSD is malfunctioning/dying then benchmarks will suffer


• Faulty/outdated SSD firmware can cause issues so update to latest firmware.


• The SATA drivers for your motherboard might be faulty or too old to handle SSDs properly so make sure to update those


• TRIM is hugely important for older SSDs whose controllers have a poor garbage collection routine


• Vista does not support TRIM so hopefully your SSD can clean itself up