5 Replies Latest reply: Jun 25, 2013 1:13 PM by Levi Pereira RSS

    asm vs raid 1+0

    Santosh Pradhan

      Hi ,

      We have installed oracle 11r2 enterprize edition on IBM AIX 7.1

      Storage RAID 1+0

      ASM Redundancy  EXTERNAL

       

      RAID 1+0 means  mirroring and striping at storage level and ASM will also go for STRIPING .

       

      So what will exactly happens when data is stored in database  ?

      Who will stripe first ?ASM or Storage

      Will this DOUBLE striping lead to performance issue ?

       

      Kindly explain ............

        • 1. Re: asm vs raid 1+0
          Mihael

          For diskgroup with external redundancy ASM only distributes extents of files among all disks. If you have one disk (one logical volume created on storage), there will be no distribution.

          • 2. Re: asm vs raid 1+0
            Santosh Pradhan

            Hey Thanx for rply,

            I hv undrstood that in my case ASM will not b performing mirroring . ASM will do only striping .

            But my  doubt is , in RAID 1+0 configuration when striping will come in picture ,

            Who will stripe first ?ASM or Storage

            Will this DOUBLE striping lead to performance issue ?

             

            answr wil be appreciated

            • 3. Re: asm vs raid 1+0
              Mihael

              If you have more than one ASM disk, ASM will first stripe data by au size (coarse-grained) or by 128K (fine-grained). Then storage will stripe again. Based on your storage stripe size, ASM au size and database workload, this can affect performance. To avoid this, configure only one logical volume on storage level in order to have only one ASM disk. Or configure pairs of disk as RAID 1 on storage level so that ASM will do striping.

              • 4. Re: asm vs raid 1+0
                Dude!

                There is a common misunderstanding here. ASM is not RAID.

                 

                ASM is a software based solution to provide data redundancy, but it is not RAID. Unlike RAID, which works on basis of disks and blocks, ASM works on the basis of file extents (AU units) distributed on available free space of disk failure groups.  ASM provides more configuration and space management flexibility than RAID. For instance, you can add and remove disks to change the capacity of volumes (disk groups) without the need to rebuild your storage, which is not possible under RAID.

                 

                From a performance, redundancy and space utilization aspect, multiple ASM failure groups, which can consist of single or multiple disks, can provide a better value for money than any RAID solution, in particular for Oracle Database products. ASM knows about Oracle database files and uses different and optimal stripping sizes based on file templates.

                 

                ASM in combination with RAID solutions provides additional performance and redundancy options. ASM is standard and recommended to store Oracle database files. RAID and ASM are complementary solutions and ASM redundancy using RAID storage provides additional benefits.

                • 5. Re: asm vs raid 1+0
                  Levi Pereira


                  Previous post by Dude is clear about RAID and ASM .. adding some useful links.


                  Oracle recommends that you use hardware RAID functionality to create LUNs.

                  http://docs.oracle.com/cd/E11882_01/server.112/e18951/asmprepare.htm#BHCDCFIH


                  See this thread

                  https://forums.oracle.com/message/9402230#9402230