10 Replies Latest reply on Jan 21, 2011 10:51 AM by cfsKC

    RAID3 Storage Capacity Loss


      The installation of RAID3 on my workstation has just been completed but I am at a loss to understand why I lost so much storage capacity.


      A seven disk (each a 1TB Samsung Spinpoint F3) RAID3 array with an Areca arc-1880ix-16 controller with a 1TB Samsung F3 Hot Swap by a "professional" from a local computer shop. Upon completion, the 7 TB array yields a total capacity of only 4.54TB.


      I expected to lose some capacity but a 35% loss seems out of line.


      1. What capacity loss can normally be expected with a RAID 3 array?
      2. If my 35% loss is out of line, what steps, other than finding a better "professional", might be considered to rectify the situation?
        • 1. Re: RAID3 Storage Capacity Loss
          ECBowen Most Valuable Participant

          Sounds like they made 1 disk a global hot spare or you are running a different raid level than you expected.




          1 person found this helpful
          • 2. Re: RAID3 Storage Capacity Loss
            Harm Millaard Level 7

            First of all, manufacurers claim 1 TB disk space, but they calculate in 1,000,000,000 bytes, so after formatting 1 TB amounts to 931 GB.


            Second, a 7 disk raid3 should yield a net storage of 6 x 931 GB = 5,586 GB or 5.46 TB.


            Now, if your professional has added a 'hot-spare', as Eric correctly assumes, the net space is only 5 x 931 GB = 4,655 GB or 4.54 TB.


            Net capacity for a raid3/5 is (n - 1) x disk size. n being the number of disks in the raid, excluding hot-spares.

            1 person found this helpful
            • 3. Re: RAID3 Storage Capacity Loss
              cfsKC Level 1

              Thank you both, but one more point if I may . . .


              The 1TB Hot Swap is in addition to the 7 disk RAID array. Does this change the calculation of the array's capacity?

              • 4. Re: RAID3 Storage Capacity Loss
                ECBowen Most Valuable Participant

                It should yes. Please post screen pic of Areca configuration utility showing the raid array.




                • 5. Re: RAID3 Storage Capacity Loss
                  cfsKC Level 1

                  Eric -


                  How do I find the Areca Configuration Utility? I'm lucky to be able to find Disk Management



                  • 7. Re: RAID3 Storage Capacity Loss
                    cfsKC Level 1

                    I did not, but I do now have MRAID ARCHTTP: installed. When I click on Launch Browser it shows:


                    MRAID screenshot.jpg

                    and I haven't a clue as to what to do next.

                    • 8. Re: RAID3 Storage Capacity Loss
                      ECBowen Most Valuable Participant

                      It's not finding the controller. Restart your system.


                      Did you restart the system and launch again?




                      • 9. Re: RAID3 Storage Capacity Loss
                        Bill Gehrke Most Valuable Participant

                        It is not at  During boot up look for the address in the controller BIOS screen

                        • 10. Re: RAID3 Storage Capacity Loss
                          cfsKC Level 1

                          Finally, I have my problem solved thanks to Eric at ADK.


                          My 8 1TB disk RAID3 array with a hot swap spare now yeilds a total capacity of 5.45TB as Harm indicated it should.


                          The person who installed my controller and set up my RAID3 system made a number of errors and omissions in the process. After much consternation, I called Eric at ADK and hired him to assist me by remote hook up. Which he did brilliantly.


                          Along the way, we discovered that the Areca controller utility utilizes a Java version which is not compatible with Windows 7, or at least as it is installed on my system. Neither the Areca download or their CD could be used to install the utility.  Eric found a workaround and got it installed properly.


                          Eric then went about updating a number of drivers on the workstation as well as adding a few which he thought appropriate to my needs. Then he set about making a number of adjustments to the set ups for the programs in my Adobe CS5 Creative Suite Master Collection. Along the way this technical boob had the opportunity to ask a number of questions and get real clarity on gaining optimum performance from my workstation.


                          Finally, Eric ran the PPBM5 benchmark test again. I was, frankly surpised that there was no appreciable increase in the speed of my workstation in dealing with the tasks which are part of that test. That, frankly, was of little importance to me as my primary goal to the security of my files.


                          I simply cannot say enough about Eric and how pleased I am to have him as a resource to turn to when the need arises. He was gracious and patient with me and tenaciously resolved to find the workaround as well as take the additional steps needed to get my system working properly.

                          Smiley clapping.gif