RE: ASM question

Amir,

From Oracle documentation: REQUIRED_MIRROR_FREE_MB, Amount of space that is required to be available in a given disk group in order to restore redundancy after one or more disk failures. The amount of space displayed in this column takes mirroring effects into account.

USABLE_FILE_MB , Amount of free space that can be safely utilized taking mirroring into account, and yet be able to restore redundancy after a disk failure (my comment: this number can become negative for example in case of disk failures)

A better explanation of the implications of this in http://blog.oracloid.com/2006/05/vldb-with-asm/

Cheers,
L.

-----Original Message-----
From: oracle-l-bounce_at_freelists.org
[mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Hameed, Amir Sent: Friday, February 23, 2007 7:14 PM
To: oracle-l_at_freelists.org
Subject: ASM question

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

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