6 Replies Latest reply: Sep 8, 2012 3:50 AM by udayjampani RSS

    What is the effective available disk space in exadata

    udayjampani
      Hi ,
      Greetings of the day ,


      Is the below understanding correct ?


      In a half rack machine there are 7 cells and all are mirror copies of other , so the effective storage space = disk space in one cell .

      Further if we have normal redundancy in each cell , then the effective storage space of the whole exadata will be half of the disk space in the cell.


      Is there any rule that all the cells must have equal disk space?


      In ASM perspective ,

      Is there any rule like all the all the fail groups ( 2 or 3 depends on the redundancy level) must have equal size with in a disk group?
        • 1. Re: What is the effective available disk space in exadata
          damorgan
          Is your first statement intended to indicate that you think 7x storage is the same amount of space as 1X storage? Or just that they must have the same disks ... high performance or high capacity?
          • 2. Re: What is the effective available disk space in exadata
            andy.colvin
            Each cell is not a full copy of the other cells. ASM diskgroups on Exadata utilize each cell as a failgroup, meaning that no 2 copies of an allocation unit are placed on the same cell. A half rack of high capacity storage (3TB drives) has 252TB of raw space (12 disks * 7 cells) ~126TB of usable space with normal redundancy, and ~84TB of usable space in high redundancy. As far as disk sizes, on ASM you generally want all disks to be the same size to keep everything balanced evenly. I have a short writeup on Exadata diskgroup storage at http://blog.oracle-ninja.com/2011/12/exadata-diskgroup-planning
            • 3. Re: What is the effective available disk space in exadata
              udayjampani
              What i mean is at ASM level they were all different failgroups, so the effective storage space = Space in one exadata cell.

              Correct me if i'm wrong?
              • 4. Re: What is the effective available disk space in exadata
                udayjampani
                andy.colvin wrote:
                no 2 copies of an allocation unit are placed on the same cell.
                How many copies will be stored ?
                Normal redundancy - 2copies
                High redundancy - 3copies

                Can i say like there is 1 to 1 relationship between cell and fail group?

                How the striping happens in 12 cell disks of each cell?

                How many cell failures can be tolerated?
                • 5. Re: What is the effective available disk space in exadata
                  Dave M.-Oracle
                  Hi udayjampani -

                  The My Oracle Support Community which covers all support related questions about EXADATA is available under: https://communities.oracle.com/portal/server.pt/community/exadata_general/360

                  Have you ever visited the Community to exchange, learn, share and get answers to your support related questions?

                  The answer to your queries are available on the My Oracle Support Community for Exadata
                  https://communities.oracle.com/portal/server.pt?open=514&objID=224&mode=2&threadid=429976&aggregatorResults=T429976T429910T426835T426876T422126T424767T422172T415389T420356T416710&sourceCommunityId=360&sourcePortletId=268&doPagination=true&pagedAggregatorPageNo=1&returnUrl=https%3A%2F%2Fcommunities.oracle.com%2Fportal%2Fserver.pt%3Fopen%3Dspace%26name%3DCommunityPage%26id%3D23%26psname%3DOpener%26psid%3D22%26cached%3Dtrue%26in_hi_userid%3D173523%26control%3DSetCommunity%26PageID%3D0%26CommunityID%3D360%26&Portlet=All%20Community%20Discussions&PrevPage=Communities-CommunityHome

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                  • 6. Re: What is the effective available disk space in exadata
                    udayjampani
                    Now it is clear,,,


                    Thank you so much Dave...