ASM fast mirror resync is used to efficiently deal with transient disk failures

Asm fast mirror resync is used to efficiently deal

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ASM fast mirror resync is used to efficiently deal with transient disk failures. 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 modified during the outage. Note that the tracking mechanism uses one bit for each modified extent and is very efficient. 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 outages that ASM will tolerate while still being able to resynchronize after the failed disk is repaired. The default setting for the DISK_REPAIR_TIME attribute is 3.6 hours. If a disk remains offline longer than the time specified by the DISK_REPAIR_TIME attribute, the disk is dropped from the disk group and the disk group is rebalanced. Numerous enhancement have been made to ASM fast mirror resync in Oracle Database 12 c . The following pages introduce those enhancements. Copyright © 2014, Oracle and/or its affiliates. All rights reserved. ASM Fast Mirror Resync: Review Enabled when COMPATIBLE.RDBMS >= 11.1 ASM redundancy used P P P S S S Disk access failure (disk offline) P P P S S S Failure time < DISK_REPAIR_TIME ; Accessible extents can be modified P ## P P S S ** S Disk becomes accessible; modified extents synchronized P ## P ** P S ## S ** S 1 2 3 4 Primary extent Secondary extent Screen reader hint: This slide contains a diagram that is explained in the speaker notes. Oracle University and Error : You are not a Valid Partner use only THESE eKIT MATERIALS ARE FOR YOUR USE IN THIS CLASSROOM ONLY. COPYING eKIT MATERIALS FROM THIS COMPUTER IS STRICTLY PROHIBITED
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ASM allows administrators to control the amount of resources that are dedicated to disk resync operations. This is conceptually similar to the capability in previous versions, which allowed administrators to control the amount of resources that are dedicated to a disk group rebalance operation. To control the amount of resources dedicated to disk resync operations, administrators can specify a power limit setting that is an integer value between 1 and 1024. Because lower numbers dedicate few resources, the operation takes longer but has minimal impact on other work. Higher values allow the operation to finish quicker at the cost of potentially impacting other work. To specify the power limit setting for a resync operation, use the ALTER DISKGROUP SQL command or the ASMCMD ONLINE command. Examples of both commands are shown in the slide. Oracle Database 12 c : Oracle Automatic Storage Management Administration 4 - 57 Copyright © 2014, Oracle and/or its affiliates. All rights reserved. Controlling the Resources Used by Resync Power limit can be set for disk resync operations: It is conceptually similar to the power limit setting for disk group rebalance.
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