2 Replies Latest reply: Mar 13, 2012 10:35 AM by Talip Hakan Ozturk RSS

    What is ASM disk rebalancing?What is significance of rebalance power?

    udayjampani
      What is ASM disk re-balancing?
      What is significance of re-balance power?
      In what situations we need to re-balance the disk?
      In what situation asm instance will automatically re-balance the disk?
        • 1. Re: What is ASM disk rebalancing?What is significance of rebalance power?
          Talip Hakan Ozturk
          Rebalancing a disk group moves data between disks to ensure that every file is evenly spread across all of the disks in a disk group. ASM automatically initiates a rebalance after storage configuration changes, such as when you add, drop, or resize disks. The power setting parameter determines the speed with which rebalancing operations occur.

          http://docs.oracle.com/cd/B28359_01/server.111/b31107/asmdiskgrps.htm#BABCCEAB


          Talip Hakan Ozturk
          http://taliphakanozturken.wordpress.com/
          • 2. Re: What is ASM disk rebalancing?What is significance of rebalance power?
            Hans Forbrich
            ASM attempts to spread the data evenly across all disks in a disk group. It does this on a 'file' basis, and in the database, a 'datafile' assigned to a tablespace is a 'file'.

            So when you add a new datafile, ASM tries to spread that file across all available disks in the diskgroup.

            If you add another disk, or if you remove a disk (or it fails) ASM will automatically re-spread all files across the new disk layout for that group. This re-spread is called 'rebalance', which happens at disk add/remove time.

            Normally a separate process is fired up to do that rebalance. This will take a certain amount of time. If you want it to happen faster, fire up more processes. You tell ASM it can add more processes by increasing the rebalance power.