Oracle DBA – A lifelong learning experience

Balancing ASM disks in one command – the benefits

Posted by John Hallas on June 5, 2012

As a response to my previous post about adding and dropping ASM disks with one command Emre Baransel asked a question as to whether it was more efficient or not to do it as one or two commands. It was easier to add  a second post complete with screen shots rather than just a simple reply.

My test system was a 3.5Tb database spread across 10 512Gb luns.

The first choice was to add and drop using a single command

alter diskgroup data add disk '/dev/oracle_3par/rdisk5008' drop disk 'DATA_0000' rebalance power 5;

GROUP_NUMBER OPERA STATE         POWER     ACTUAL      SOFAR   EST_WORK   EST_RATE EST_MINUTES ERROR_CODE
------------ ----- -------- ---------- ---------- ---------- ---------- ---------- ----------- --------------------------------------------
           1 REBAL RUN               5          5       6882     419874      20621          20
GROUP_NUMBER OPERA STAT      POWER     ACTUAL      SOFAR   EST_WORK   EST_RATE EST_MINUTES ERROR_CODE
------------ ----- ---- ---------- ---------- ---------- ---------- ---------- ----------- --------------------------------------------
           1 REBAL RUN           5          5      10064     419880      24541          17

This was at power level 5 and the actual work (number of allocation_units to be moved) was ~420k.

 

 

 

 

 

Note the  throughput on the HBA adapters generated by 5 asm_arb+ASM1 processes

Changing the power level to 9 causes another 4  arb processes to start  and the HBA throughput increases significantly (this was a test system on a Bank Holiday, not to be recommended on a production system)

 

 

 

 

 

The second method was to drop and add in separate commands, all with the same power level of 5

alter diskgroup data add disk '/dev/oracle_3par/rdisk5008' rebalance power 5;

GROUP_NUMBER OPERA STAT      POWER     ACTUAL      SOFAR   EST_WORK   EST_RATE EST_MINUTES ERROR_CODE
------------ ----- ---- ---------- ---------- ---------- ---------- ---------- ----------- --------------------------------------------
           1 REBAL RUN           5          5       3503     376381      10219          35
          

alter diskgroup data drop disk 'DATA_0000' rebalance power 5;

GROUP_NUMBER OPERA STAT      POWER     ACTUAL      SOFAR   EST_WORK   EST_RATE EST_MINUTES ERROR_CODE
------------ ----- ---- ---------- ---------- ---------- ---------- ---------- ----------- --------------------------------------------
           1 REBAL RUN           5          5     196638     378433      19355           9

As can be seen, the overall work to be done is ~750K allocation units to be moved around which is almost double the original workload.

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3 Responses to “Balancing ASM disks in one command – the benefits”

  1. Narendra said

    John,

    Thanks for these 2 posts (claim and evidence). Documentation does make a reference to this here but could not find the WHY part there

  2. g10chy said

    Hi, thanks for this post as you have saved me massive amounts of time. Can I ask what the program you are using to see the HBA throughput?
    Thanks,
    Chris

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