3 Replies Latest reply: Dec 24, 2012 1:35 PM by Catch_22 RSS

    several questions about oracle ASM in 11gR2.

    872581
      Hi, all.

      The db is 11.2.0.3 on a linux machine.

      I have several questions about oracle ASM functionality.

      ------------------------------------------------------------------------------------
      1. V$ASM_DISKGROUP.ALLOCATION_UNIT_SIZE is the stripe size in bytes??

      2. V$ASM_DISK.DISK_NUMBER is unique to a physical disk??

      3. if the second question is the case,
      disk_number=0 (a physical disk) has 14 partition on it.
      And each partition belongs to several diskgroups.

      Is ths right??
      with q1 as (
           select /*+ use_hash(b,a) */
                disk_number,b.group_number,b.name,a.path,sum(os_mb) tot_size ,count(*) cnt
           from v$asm_disk a, v$asm_diskgroup b
           where a.group_number=b.group_number
           group by disk_number,b.group_number,b.name,a.path
           order by disk_number,b.group_number,b.name
      )
      select disk_number,group_number,name,path,tot_size,
             sum(tot_size) over (partition by disk_number) disk_size,
             sum(cnt) over (partition by disk_number) parition_cnt_per_disk
        from q1
        order by q1.disk_number,group_number
      
      DISK_NUMBER     GROUP_NUMBER     NAME     PATH     TOT_SIZE     DISK_SIZE     PARITION_CNT_PER_DISK
      0     1     ARCH     /dev/raw/raw100     53256     454460     14
      0     2     AAAREDO1     /dev/raw/raw111     10240     454460     14
      0     3     AAAREDO2     /dev/raw/raw113     10240     454460     14
      0     4     CRS     /dev/raw/raw83     3000     454460     14
      0     5     BBBDATA1     /dev/raw/raw10     50232     454460     14
      0     6     BBBDATA2     /dev/raw/raw41     50232     454460     14
      0     7     BBBREDO1     /dev/raw/raw1     10240     454460     14
      0     8     BBBREDO2     /dev/raw/raw3     10240     454460     14
      0     9     CCCDATA1     /dev/raw/raw75     76400     454460     14
      0     10     CCCDATA2     /dev/raw/raw165     51300     454460     14
      0     11     CCCREDO1     /dev/raw/raw118     10240     454460     14
      0     12     CCCREDO2     /dev/raw/raw120     10240     454460     14
      0     13     CCCDATA1     /dev/raw/raw125     51300     454460     14
      0     14     BBBDDATA     /dev/raw/raw71     57300     454460     14
      
      .
      .
      .
      Thanks in advance..
      Best Regards.

      Edited by: 869578 on 2012. 12. 23 오후 10:05
        • 1. Re: several questions about oracle ASM in 11gR2.
          Catch_22
          1. No. The stripe size always equals 128 KB in any configuration. ASM uses fine or coarse-grained striping depending on ASM templates. Files like the controlfile are fine-graind, meaning the stripe size is always 128 KB. Other files use coarse striping where the stripe size is equal to the effective AU size. (http://docs.oracle.com/cd/E11882_01/server.112/e18951/asmcon.htm#BABCGDBF)

          2. No. Its a number assigned to the disk within its disk group.
          (http://docs.oracle.com/cd/E14072_01/server.112/e10820/dynviews_1022.htm)

          Edited by: Dude on Dec 24, 2012 11:26 AM
          • 2. Re: several questions about oracle ASM in 11gR2.
            rcc50886
            1. No. The stripe size always equals 128 KB in any configuration.
            (http://docs.oracle.com/cd/E11882_01/server.112/e18951/asmcon.htm#BABCGDBF)
            That is not a true statement. Please read the document, the stripe size depends upon what method of striping we using (fine-grained or coarse-grained)

            --from the same oracle document:

            To stripe data, Oracle ASM separates files into stripes and spreads data evenly across all of the disks in a disk group. The fine-grained stripe size always equals 128 KB in any configuration; this provides lower I/O latency for small I/O operations. The coarse-grained stripe size is always equal to the AU size (not the data extent size).

            --are we using fine grained or coarse-grained ? and how to change the striping method (using TEMPLATES)

            http://docs.oracle.com/cd/E11882_01/server.112/e16102/asmfiles.htm#g2223792


            also see following:

            http://oracletechlovers.blogspot.com/2012/06/asm-differences-between-corse-and-fine.html
            • 3. Re: several questions about oracle ASM in 11gR2.
              Catch_22
              Thanks for pointing this out. I correct the mistake.