Oracle DBA – A lifelong learning experience

ASM – Adding and dropping disks in one command

Posted by John Hallas on May 29, 2012

One of the possibilities within ASM that is not widely documented is the opportunity to add disks, drop disks and set the rebalance power all in one command.

One might wonder when you might be both adding and dropping disks simultaneously from the same disk group. Recently we have been migrating to a new storage array and this command comes in very useful in that situation

alter diskgroup data add disk '/dev/oracle/disk100','dev/oracle/disk101','dev/oracle/disk102'

drop disk '/dev/oracle/disk197','dev/oracle/disk198','dev/oracle/disk199'

rebalance power 5;


5 Responses to “ASM – Adding and dropping disks in one command”

  1. Hi John. Thanks for the information. Normally if i run “add disk” and “drop disk” commands consecutively, it first finishes the rebalance of “add disk” command then starts to rebalance operation of “drop disk” command. Did you check asm’s rebalance behaviour if we run add and drop in one command?

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  3. Kalid said

    I am in the same position you just described. I am about to move my database to new storage. I have 2 options:
    1. to add new storage as disks to the same diskgroup then drop the old ones. Which will allow me to do it while database still online or
    2. RMAN backup and move database to new storage but requires down time.
    I was looking online to explore more option number 1 and I am glad I found yours. How big was your database? did you do this while database is open? how long did it take? did it affect performance? the rebalance power command did you try other options than 5 or what’s your recommendation for that?
    Sorry for the too many questions, but I highly appreciate your help

    • John Hallas said

      We went for an outage and the big bang approach of using a high PB level 8 – IIRC – the slight complexity ws that this is a 10g database uisng 11G ASM and we had seen a coupe eof funnies when adding disk in the past so we decided to get the outage -I think it was about 2 hours in total but I can find out and post back.
      I think either option is fine but this system is very busy 7 days a week so we felt an outage was best. If there is low disk activity then the trickle feed approach would work but would take forever, especially when you might need a change control to cover the work.

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