SSD suffers when controller set to RAID.

Hey guys, I just got my new Samsung 840 Pro SSD and although the write speeds are good, I am geting less than 50% advertised in read speeds. I've been troubleshooting for hours now and can't get this drive to perform even close to its advertised speed.

I have a new Gigabyte GA-z87-oc board with 1 drive controller built in (6x Sata 3). I know that ACHI needs to be enabled for maximum performance but I also have to setup a RAID5 with 3 HDDs, of course using the same, sole controller on the MB.

So in my bios I have 3 options for the Drive controller: IDE, AHCI, and RAID. I set it to RAID.

I then unplugged all drives and plugged in the SSD making sure to use the SATA cable that came with new motherboard (labeled SATA 6Gb/s).

Installed Windows 8.1 got all updates and drivers. All is well. Also verified TRIM was active.

Then powered off and plugged in the 3 HDDs and did the Ctrl+I when prompted and setup my RAID 5. Got Windows to recognize the RAID5 setup so all looks good.

However, using Samsung's utility to test the SSD, I am getting very poor results. See screenshots.


Notice in it states AHCI Mode "Deactivated" and SATA Interface N/A.

Please tell me that I'm wrong when I make the assumption that for full SSD speed I need to go full AHCI and lose my RAID completely. Or stick with my RAID setup and get 50% performance reduction as a result with my SSD.

Thanks so much in advance for any assistance!

***Note, I decided to try to go back to AHCI to retest my SSD by itself but ended up with a bluescreen.

After setting the controller mode to RAID, have you tried creating the array in the RAID BIOS, then installing Windows to the SSD w/ all 4 drives already connected? How about installing Windows to the SSD w/ all 4 drives connected, the controller mode set to either RAID or AHCI, then creating the RAID 5 array from within the Disk Management snap-in?

You may have to ditch the RAID functionality and stick with AHCI, depending on the chipset used for the SATA controller ports.

I can only find a Z87-OC Force, or a Z87x-OC on the Gigabyte website. Force seems to have 6 Intel SATA ports and 4 Marvell. If this is your board, you might try to use the SSD on the Intel Ports in AHCI mode, and the 4 mechanical drives on the Marvell ports in the Raid configuration you want.

I don't know if this has changed with newer chipsets, but the older x58 chipsets from Intel with the most recent chipset drivers should support SSD in AHCI mode even if set to RAID mode in the bios. Older Intel chipset drivers (I've long forgotten which version) do not support this, so make sure you have latest chipset drivers from the Intel website.

Also, if all you did was try the SSD drive by itself AFTER you had installed Windows and switch to AHCI mode, you're either going to have to reinstall Windows while in AHCI mode, or make a registry edit before you switch to AHCI mode.

http://forums.guru3d.com/showthread.php?t=313676

To put it simply RAID has all the functions of AHCI built into it and you should see little to no difference in SSD performance in one configuration or the other.

Your board has two SATA6 controllers. Try using the Marvell controller in AHCI for the SSD on its own and leave the hard drives on the Intel ports since the Marvell controller doesn't support RAID 5 you wont be able to put the HDDs on it leaving the SSD on the Intel ports.

Make sure you have the latest drivers installed for both the Intel and the Marvell controllers as well as the chipset.

By the way... I hope you are using decent hard drives for that RAID 5 (enterprise type drives) because if you ever need to rebuild it and encounter a URE, you're done.

Thanks for the replies and offers of help. Ultimately here is what i did to get the issue resolved.

1. Set controller in bios to RAID
2. Plugged in all drives and did the Ctrl+I and created the RAID.
3. Went back into bios and changed storage controller back to AHCI.
4. Unplugged all drives except for SSD
5. Installed Windows 8.1 on SSD and downloaded all windows updates / drivers.
6. Turned PC off and plugged all drives back up (Kept Controller set to AHCI in bios).
7. Booted machine and now my RAID is still configured and my SSD utility shows SATA 3 and AHCI set and I am getting full performance!

Werid, but that is the way I had to do it to get my SSD to full speed.

Thanks again, folks!

I'm using Z87X-OC with 1x SSHD ( Seagate 500GB ) + 1x SSD ( Samsung 840 Pro ) + 2x HDD in RAID1. RAID set in BIOS. No additional settings.
I installed system with only SSHD connected but RAID enabled in BIOS. Later I added 2x HDD and made RAID. Samsung 840 Pro has been added at the end and performance is like it should be. I'm using Win7 Pro x64.
Performance can be lower if you are using MS AHCI driver which is also working as RAID driver. Best is to get latest Intel RAID driver and all chipset drivers.