Enabled when COMPATIBLE.RDBMS >= 11.1
Whenever ASM is unable to write an extent, ASM takes the associated disk offline. If the corresponding disk group uses ASM mirroring (NORMAL or HIGH redundancy), at least one mirror copy of the same extent exists on another disk in the disk group.
Before Oracle Database 11g, ASM assumed that an offline disk contains only stale data and no longer reads from such disks. Shortly after a disk is put offline, ASM drops it from the disk group by re-creating the extents allocated to the disk on the remaining disks in the disk group using mirrored extent copies. This process is quite resource intensive and can take hours to complete. If the disk is replaced or the failure is repaired, the disk must be added again and another rebalance operation must take place.
ASM fast mirror resync significantly reduces the time required to resynchronize a transient failure of a disk. When a disk goes offline following a transient failure, ASM tracks the extents that are modified during the outage. When the transient failure is repaired, ASM can quickly resynchronize only the ASM disk extents that have been affected during the outage.
Using ASM fast mirror resync, the failed disk is taken offline but not dropped if you have set the DISK_REPAIR_TIME attribute for the corresponding disk group. The setting for this attribute determines the duration of disk outage that ASM will tolerate while still being able to resynchronize after you complete the repair. Note that the tracking mechanism uses one bit for each modified extent and is very efficient.
Whenever ASM is unable to write an extent, ASM takes the associated disk offline. If the corresponding disk group uses ASM mirroring (NORMAL or HIGH redundancy), at least one mirror copy of the same extent exists on another disk in the disk group.
Before Oracle Database 11g, ASM assumed that an offline disk contains only stale data and no longer reads from such disks. Shortly after a disk is put offline, ASM drops it from the disk group by re-creating the extents allocated to the disk on the remaining disks in the disk group using mirrored extent copies. This process is quite resource intensive and can take hours to complete. If the disk is replaced or the failure is repaired, the disk must be added again and another rebalance operation must take place.
ASM fast mirror resync significantly reduces the time required to resynchronize a transient failure of a disk. When a disk goes offline following a transient failure, ASM tracks the extents that are modified during the outage. When the transient failure is repaired, ASM can quickly resynchronize only the ASM disk extents that have been affected during the outage.
Using ASM fast mirror resync, the failed disk is taken offline but not dropped if you have set the DISK_REPAIR_TIME attribute for the corresponding disk group. The setting for this attribute determines the duration of disk outage that ASM will tolerate while still being able to resynchronize after you complete the repair. Note that the tracking mechanism uses one bit for each modified extent and is very efficient.
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