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2 Replies Latest reply: Mar 13, 2012 8:35 AM by Talip Hakan Ozturk RSS

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

udayjampani Newbie
Currently Being Moderated
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 Oracle ACE
    Currently Being Moderated
    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 Oracle ACE Director
    Currently Being Moderated
    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.

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