What Happens When Disk Errors Occur?

Oracle ASM performs bad extent repair for read errors caused by hardware errors. The disks stay online, and no alerts are sent.

When a disk fails:

The Oracle ASM disks associated with it are dropped automatically with the FORCE option, and then an Oracle ASM rebalance restores data redundancy.
The blue LED and the amber LED are turned on for the drive, indicating that disk replacement can proceed. The drive LED stays on solid. See "LED Status Descriptions" for information about LED status lights during predictive failure and poor performance.
The server generates an alert, which includes specific instructions for replacing the disk. If you configured the system for alert notifications, then the alert is sent by email to the designated address.

When a disk has a faulty status:

The Oracle ASM disks associated with the grid disks on the physical drive are dropped automatically.
An Oracle ASM rebalance relocates the data from the predictively failed disk to other disks.
The blue LED is turned on for the drive, indicating that disk replacement can proceed.

When Oracle ASM gets a read error on a physically-addressed metadata block, it does not have mirroring for the blocks:

Oracle ASM takes the disk offline.
Oracle ASM drops the disk with the FORCE option.
The storage server software sends an alert stating that the disk can be replaced.