The Oracle 11gR2 Automatic Storage Managament Administrator's Guide says:
When Oracle ASM allocates an extent for a mirrored file, Oracle ASM allocates a
primary copy and a mirror copy. Oracle ASM chooses the disk on which to store the
mirror copy in a different failure group than the primary copy.
It also says:
If you omit the failure group specification, then Oracle ASM automatically
places each disk into its own failure group, except for disk groups containing disks on
Oracle Exadata cells.
My question is for the following scenario how ASM will create failure groups:
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In my server when there is one disk controller and one physical hard disk having many logical volumes and created disk groups.
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When server is having two controller card and two or more hard disks with logical volumes created and used for diskgroups.
My main question is, I want to understand how this ASM decides failgroups? Please some one can guide
Best Answer
As the official documentation says, unless you specify failure groups explicitly, ASM will place each disk into its own failure group (it doesn't have any knowledge about your HW infrastructure).
Note that Oracle doesn't recommend using an OS LVM with ASM.