9 Replies Latest reply: Mar 16, 2013 6:36 PM by Levi Pereira RSS

    ASM Rebalancing

    941744
      Hi ASM Team,


      I ts know that rebalancing occurs when ver a disk is added or removed ora some physical action is performed..its ok

      But my question here is is there any other operation like adding/deleting/modifying a datafile that will lead to rebalancing??
        • 1. Re: ASM Rebalancing
          Hungry DBA
          Hi,

          There is no rebalancing happen for adding/deleting/modifying a datafile. (if you want to verify then check in v$asm_operation view, at the time of adding/deleting/modifying a datafile), you will come to know.

          Rebalancing is purely feature of ASM and work at Disk Level ONLY.


          I hope this helps you :)

          Thanks,
          Manish Nashikkar
          • 2. Re: ASM Rebalancing
            941744
            is there any other operation except disk addition/removal/resize, rebalancing occurs???
            • 3. Re: ASM Rebalancing
              Hungry DBA
              No. Rebalancing only happen at the time of addition/removal/resize of disk in ASM Diskgroup.

              Thanks,
              Manish Nashikkar
              • 4. Re: ASM Rebalancing
                941744
                Will wait for Hussein,Aman to comment on this to be sure on this.....


                Thanks for your help...
                • 5. Re: ASM Rebalancing
                  Levi Pereira
                  938741 wrote:
                  Hi ASM Team,


                  I ts know that rebalancing occurs when ver a disk is added or removed ora some physical action is performed..its ok

                  But my question here is is there any other operation like adding/deleting/modifying a datafile that will lead to rebalancing??
                  About Files over ASM (BALANCE):

                  The contents of Oracle ASM files are stored in a disk group as a set, or collection, of extents that are stored on individual disks within disk groups. Each extent resides on an individual disk.
                  Oracle ASM data distribution policy is capacity-based. So, when you create/resize/delete a datafile Oracle ASM will create/delete a extent in each ASMDISK of that Diskgroup to maintain data distribution equal in all ASMDISK.

                  This operation is not rebalance, but it's data distribution or only "BALANCE"


                  About Rebalance Operation (REBALANCE):

                  Rebalance occurs when something changes characteristic of a balanced Diskgroup unbalancing it, so you will need REBALANCE it.
                  Operation that cause UNBALANCE of ASMDISK are addition/removal/resize of ASMDIKS in ASM Diskgroup or change of attribute CONTENT.TYPE (11.2.0.3 only)

                  Rebalance is different of Balance, don't confuse it.

                  Levi Pereira
                  • 7. Re: ASM Rebalancing
                    Hungry DBA
                    Thanks Levi for detailed explaination,

                    So Conclusion could be,

                    *ASM Rebalance feature is more of Striping of data (could be called distribution) across all disks when add/delete/resize takes place.

                    * While adding/deleting/resizing datafile seen ARB0-ARB9 Processes idle and doesn't perform any rebalance operation at disk level. (instead it happen at extent level)

                    Correct me if I'm wrong...

                    Thanks,
                    Manish Nashikkar

                    Edited by: Hungry DBA on Mar 15, 2013 10:33 PM
                    • 8. Re: ASM Rebalancing
                      onedbguru
                      938741 wrote:
                      Will wait for Hussein,Aman to comment on this to be sure on this.....


                      Thanks for your help...
                      Not to be rude -well yes, I will be rude... if you were to actually read the documentation you would see that the question has been asked and answered and I doubt Aman knows more about it than what has been said. Some of us here have been using ASM since it was introduced many years ago. If you don't like the answers, then it would behoove you to research the answer for yourself... A simple google search turns up a LOT of hits on the subject. It you can't use google, then you may need to find another line of work.

                      Now, there are several Oracle Press books on the subject, one that would shed more light was written by some of the developers called "Automatic Storage Management - Under-the-Hood & Practical Deployment Guide" by Nitin Vengurlekar, Murali Vallath and Rich Long with a forward by Bill Bridge, the ASM Architect.
                      • 9. Re: ASM Rebalancing
                        Levi Pereira
                        right.