7 Replies Latest reply on Aug 16, 2013 10:32 PM by geohei

    Drawbacks of RAID versus AHCI




      Gigabyte GA-Z77X-UD5H / F14


      On that mobo, the Intel chipset is in charge of 2 SATA3 and 4 SATA2 ports.


      I use 2 of the SATA2 ports for RAID and have RAID selected for the Intel chipset in UEFI.

      On port 0, I use a Samsung SSD 840.


      Now ... the Samsung software Magician reports that AHCI is disabled for the SATA, which is correct.


      But as far as I know, RAID includes all benefits of AHCI.

      Is that correct?


      These would be NCQ, TRIM, ... ?



        • 1. Re: Drawbacks of RAID versus AHCI

          No answer ...

          Was the question not clear? Shall I rephrase?



          • 2. Re: Drawbacks of RAID versus AHCI
            Ziad Aghar

            RAID includes all the functionalities of AHCI "just like you said".

            Recently TRIM has been supported under RAID levels. Native Command Queuing improves the performance of certain few SSDs. However the Samsung 840 isn't affected with or without NCQ.

            Typical users would not need it, although it does not hurt to have it there.

            • 3. Re: Drawbacks of RAID versus AHCI

              You say that recently, TRIM is supported. I use Does this version support TRIM already?


              Besides this ... is this a normal performance of the Samsung SSD?3_magician_raid_performance_after_trim.png

              • 4. Re: Drawbacks of RAID versus AHCI
                Ziad Aghar

                Yes, your driver version supports TRIM under RAID. By recently I meant that at first TRIM wasn't functional under RAID.

                The Samsung 840 pro is among the best & fastest available SSDs on the market today. You made the proper choice by buying the pro version.

                Just take it easy on the benchmarks . You don't want to make those unnecessary writes which might affect performance on the long run.

                • 5. Re: Drawbacks of RAID versus AHCI

                  Yes, but what about "Random Write IOPS"?

                  3 out of 4 performance are where they should be, but "Random Write IOPS" is off?

                  Do you have any explanation for this?

                  • 6. Re: Drawbacks of RAID versus AHCI
                    Ziad Aghar

                    Your IOPS is not off "actually it's good"

                    Input Output Operations Per Second "IOPS" is a bit complicated thing to explain. It depends on the drive's storage capacity, the benchmark itself that is being ran, etc... Not to mention that published numbers doesn't guarantee real world scenarios. Do note that HDDs top it out at 100 IOPS.


                    Also, it says up to 90K & yours was at 62K. In real world apps you won't realize any difference. Albeit, I know that's not what you want to hear, you want to know why your drive isn't topping the 90K.


                    Like I said this number varies according to many things but, still 60K is more than you & I will ever need. Moreover, most SSD manufacturers focus on read speeds rather than write speeds to replicate real world scenarios.

                    In a nutshell, your drive utilize something called toggle NAND, which is a mixture of both. Yet they focus on read speeds cause that's what we do most of the time. Hence, the read speeds are higher in IOPS

                    1 of 1 people found this helpful
                    • 7. Re: Drawbacks of RAID versus AHCI

                      OK ... thanks a lot for the explanations!

                      Bottomline ...

                      1. TRIM and NCQ is supported with my IRST

                      2. My SSD IOPS benchmark is fine.