Re: ASM question

Amir,
when you have 2 failure groups, if you loose one of them, ASM tries to create a mirror of the remaining data in the same FG. So, as your diskgroup is 10G, you need to keep 5G free in case it needs to duplicate the data (that's the REQUIRED_MIRROR...). As for the usable_file_mb, it says that you can safely use 7G and have almost 1/2 of that left in case you need to mirror the data in case of disk failure.

rgds

On 2/23/07, Hameed, Amir <Amir.Hameed_at_xerox.com> wrote:
>
> Hi Folks,
> I have a 10.2.0.2 ASM instance running on Solaris 9 with the following
> scenario:
>
> 1. All raw disk slices are 5GB in size
>
> 2. I have created a normal redundancy ASM diskgroup with two failure
> groups as shown below:
> SQL> create diskgroup data normal redundancy
> failgroup failgroup_1
> disk '/dev/vx/rdsk/ux016_RAW/volraw_01'
> failgroup failgroup_2
> disk '/dev/vx/rdsk/ux016_RAW/volraw_02'
> /
>
> When I run the sql statement, as shown below, I see the following
> output:
> SQL> select GROUP_NUMBER GROUP#, NAME, STATE, TOTAL_MB, FREE_MB,
> REQUIRED_MIRROR_FREE_MB REQ_MIRR_FREE_MB, USABLE_FILE_MB
> from V$ASM_DISKGROUP;
>
> GROUP# NAME STATE TOTAL_MB FREE_MB
> REQ_MIRR_FREE_MB USABLE_FILE_MB
> ---------- -------------- --------------- ---------- ----------
> ---------------- --------------
> 1 DATA MOUNTED 10240 10138
> 0 5069
>
> So, the total size of the DG is 10GB with Usable space of 5GB. Because
> the group is mirrored 1:1, the REQ_MIRR_FREE_MB is zero.
>
> 3. When I create the same group with two disks in each failover group, I
> see an output that I am not able to comprehend:
> SQL> create diskgroup data
> failgroup failgroup_1
> disk
> '/dev/vx/rdsk/ux016_RAW/volraw_01',
> '/dev/vx/rdsk/ux016_RAW/volraw_02'
> failgroup failgroup_2
> disk
> '/dev/vx/rdsk/ux016_RAW/volraw_03',
> '/dev/vx/rdsk/ux016_RAW/volraw_04'
> /
>
> SQL> select GROUP_NUMBER GROUP#, NAME, STATE, TOTAL_MB, FREE_MB,
> REQUIRED_MIRROR_FREE_MB REQ_MIRR_FREE_MB, USABLE_FILE_MB
> from V$ASM_DISKGROUP;
>
> GROUP# NAME STATE TOTAL_MB FREE_MB
> REQ_MIRR_FREE_MB USABLE_FILE_MB
> ---------- -------------- --------------- ---------- ----------
> ---------------- --------------
> 1 DATA MOUNTED 20480 20374
> 5120 7627
>
> I was hoping to see REQ_MIRR_FREE_MB of zero because I have a DG that
> contains two failure groups with each group contains two disks. I was
> also expecting to see 10GB for the USABLE_FILE_MB.
>
> Can someone please clarify how two interpret these stats.
>
> Thanks
> Amir
>
> --
> http://www.freelists.org/webpage/oracle-l
>
>
>

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