ASM DISKGROUP SHOWS USABLE_FILE_MB VALUE IN NEGATIVE
GRID DISK = ASM DISK.
When creating disk groups, ASM automatically puts all grid disks from the same storage cell into the same failgroup. The failgroup is then named after the storage cell.
[oracle@test~]$ asmcmd lsdg
State Type Rebal Sector Block AU Total_MB Free_MB Req_mir_free_MB Usable_file_MB Offline_disks Voting_files Name
MOUNTED NORMAL N 512 4096 4194304 40697856 8464936 13565952 -2550508 0 N DATA1/
MOUNTED NORMAL N 512 4096 4194304 415296 367220 138432 114394 0 Y DBFS_DG/
MOUNTED NORMAL N 512 4096 4194304 10176480 9018276 3392160 2813058 0 N RECO1/
compute sum Label total_FG of total_mb on FAILGROUP
compute sum Label total of total_mb on report
col diskgroup for a20
col failgroup for a30
col name for a30
select g.name diskgroup, d.failgroup, d.name, d.total_mb from v$asm_disk d, v$asm_diskgroup g where g.name = 'DATA1' and d.GROUP_NUMBER = g.GROUP_NUMBER order by g.name, d.failgroup;
DISKGROUP FAILGROUP NAME TOTAL_MB
-------------------- ------------------------------ ------------------------------ ----------------
DATA1 CELL01 DATA1_CD_00_CELL01 2260992
DATA1 DATA1_CD_05_CELL01 2260992
DATA1 DATA1_CD_03_CELL01 2260992
DATA1 DATA1_CD_04_CELL01 2260992
DATA1 DATA1_CD_01_CELL01 2260992
DATA1 DATA1_CD_02_CELL01 2260992
****************************** ----------------
total_FG 13565952
DATA1 CELL02 DATA1_CD_01_CELL02 2260992
DATA1 DATA1_CD_05_CELL02 2260992
DATA1 DATA1_CD_02_CELL02 2260992
DATA1 DATA1_CD_03_CELL02 2260992
DATA1 DATA1_CD_00_CELL02 2260992
DATA1 DATA1_CD_04_CELL02 2260992
****************************** ----------------
total_FG 13565952
DATA1 CELL03 DATA1_CD_02_CELL03 2260992
DATA1 DATA1_CD_05_CELL03 2260992
DATA1 DATA1_CD_01_CELL03 2260992
DATA1 DATA1_CD_04_CELL03 2260992
DATA1 DATA1_CD_03_CELL03 2260992
DATA1 DATA1_CD_00_CELL03 2260992
****************************** ----------------
total_FG 13565952
----------------
total 40697856
For DATA1 diskgroup the USABLE_FILE_MB shows value in Negative (-2550508 MB).
SQL> select name, state, type, total_mb, free_mb, required_mirror_free_mb req_free, usable_file_mb use_mb from v$asm_diskgroup where name = 'DATA1';
NAME STATE TYPE TOTAL_MB FREE_MB REQ_FREE USE_MB
------------------------- ----------- ------ ---------- ---------- ---------- ----------
DATA1 MOUNTED NORMAL 40697856 8464936 13565952 -2550508
----------
total 40697856
TOTAL_MB:- Refers to total capacity of the diskgroup
FREE_MB :- Refers to raw free space available in diskgroup in MB.
FREE_MB :- Refers to raw free space available in diskgroup in MB.
FREE_MB = (TOTAL_MB – (HOT_USED_MB + COLD_USED_MB))
REQUIRED_MIRROR_FREE_MB :- Indicates how much free space is required in an ASM disk group to restore redundancy after the failure of an ASM disk or ASM failure group.In exadata it is the disk capacity of one failure group.
USABLE_FILE_MB :- Indicates how much space is available in an ASM disk group considering the redundancy level of the disk group.
Its calculated as :-
USABLE_FILE_MB=(FREE_MB – REQUIRED_MIRROR_FREE_MB ) / 2 –> For Normal Redundancy
USABLE_FILE_MB=(FREE_MB – REQUIRED_MIRROR_FREE_MB ) / 3 –> For High Redundancy
USABLE_FILE_MB=(FREE_MB – REQUIRED_MIRROR_FREE_MB ) / 3 –> For High Redundancy
Also to note here is ASM diskgroup do not set aside the space based on reuqired_mirror_free_mb. Its merely calculated and used to derive usable_file_mb.
While reading Mos Doc Id 1551288.1 i came across some interesting terms and script which i wanted to share to everyone (atleast some of you who might not have been familiar)
Failure coverage refers to the amount of space in a disk group that will be used to re-mirror data in the event of some storage failure.
1. Disk Failure Coverage :- Refers to having enough free space to allow data to be re-mirrored (rebalanced) after a single disk failure in Normal redundancy.
2. Cell Failure Coverage :- Refers to having enough free space to allow data to be re-mirrored after loss of One entire Cell Disk.
Reserving space in the disk group means that you monitor the disk group to ensure that FREE_MB never goes below minimum amount needed for disk or cell failure coverage.
I ran the script provided in Mos Docid 1551288 and below was the output :-
Description of Derived Values: One Cell Required Mirror Free MB : Required Mirror Free MB to permit successful rebalance after losing largest CELL regardless of redundancy type Disk Required Mirror Free MB : Space needed to rebalance after loss of single or double disk failure (for normal or high redundancy) Disk Usable File MB : Usable space available after reserving space for disk failure and accounting for mirroring Cell Usable File MB : Usable space available after reserving space for SINGLE cell failure and accounting for mirroring . . . ASM Version: 11.2.0.4 . . . ---------------------------------------------------------------------------------------------------------------------------------------------------- | | | | | | | |Cell Req'd |Disk Req'd | | | | | | | |DG |Num |Disk Size |DG Total |DG Used |DG Free |Mirror Free |Mirror Free |Disk Usable |Cell Usable | | |PCT | |DG Name |Type |Disks|MB |MB |MB |MB |MB |MB |File MB |File MB |DFC |CFC |Util | ---------------------------------------------------------------------------------------------------------------------------------------------------- |DATA1 |NORMAL | 18| 2,260,992| 40,697,856| 32,233,944| 8,463,912| 14,922,547| 2,761,008| 2,851,452| -3,229,318|PASS|FAIL| 79.2%| |DBFS_DG |NORMAL | 12| 34,608| 415,296| 48,076| 367,220| 152,275| 59,425| 153,898| 107,472|PASS|PASS| 11.6%| |RECO1 |NORMAL | 18| 565,360| 10,176,480| 1,171,220| 9,005,260| 3,731,376| 703,460| 4,150,900| 2,636,942|PASS|PASS| 11.5%| ---------------------------------------------------------------------------------------------------------------------------------------------------- Cell Failure Coverage Freespace Failures Detected. Warning Message Follows. Enough Free Space to Rebalance after loss of ONE cell: WARNING (However, cell failure is very rare) . . . Script completed.
https://aprakash.wordpress.com/2014/09/17/asm-diskgroup-shows-usable_file_mb-value-in-negative/
