What happens when exadata has lost two disks?（轉）

ruanrong發表於2011-08-05
APP
Actually the question is “What happens when ASM has lost two disks in different failgroups when redundancy is normal?”[@more@]

Actually the question is “What happens when ASM has lost two disks in different failgroups when redundancy is normal?”
We’re sure that there will be no problem if we lose all of the disks in a single failgroup but in order to answer the question we have to understand how mirroring works in ASM.
In normal redundancy, mirror of each extent is written to another disk in another failgroup. This causes a partnership between these disks. As far as I’ve found out this information is kept in the x$kfdpartner table.

From the following query it seems that an extend in DATA_CD_10_CEL27 has a mirror on DATA_CD_07_CEL01. If we lose these two disks then the system has to crash.
On the other hand if we lose DATA_CD_10_CEL27 and the disks in the partner list ( 8 disks at the moment) stays alive, there will be no problem if we lose another disk.

select dg.name dg_name,
d.name disk_name,
pd.name partner_name
from x$kfdpartner p,v$asm_diskgroup dg,v$asm_disk d,v$asm_disk pd
where
p.grp=dg.group_number
and d.disk_number=p.disk and d.group_number=p.grp
and pd.disk_number=p.number_kfdpartner and pd.group_number=p.grp

and dg.name='DATA' and d.name='DATA_CD_10_CEL27';

DG_NAMEDISK_NAMEPARTNER_NAME
DATADATA_CD_10_CEL27DATA_CD_07_CEL01
DATADATA_CD_10_CEL27DATA_CD_06_CEL01
DATADATA_CD_10_CEL27DATA_CD_07_CEL25
DATADATA_CD_10_CEL27DATA_CD_06_CEL25
DATADATA_CD_10_CEL27DATA_CD_07_CEL26
DATADATA_CD_10_CEL27DATA_CD_06_CEL26
DATADATA_CD_10_CEL27DATA_CD_07_CEL28
DATADATA_CD_10_CEL27DATA_CD_06_CEL28

來自 “ ITPUB部落格 ” ，連結：http://blog.itpub.net/1933/viewspace-1053474/，如需轉載，請註明出處，否則將追究法律責任。

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