如何正确地将PVID从ASM磁盘头部除去

最新推荐文章于 2021-05-04 15:43:31 发布

宋小荣

最新推荐文章于 2021-05-04 15:43:31 发布

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分类专栏：故障处理文章标签： ASMDISK PVID

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本文介绍了解决ASMDISK上存在PVID的问题的方法，包括两种去除PVID的步骤，一种是在不停机的情况下逐个移除并清理PVID，另一种则需要停机进行操作。

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ASM磁盘元数据存放于磁盘头部，主要包含以下重要内容：

    The disks that belong to a disk group
    The amount of space that is available in a disk group
    The filenames of the files in a disk group
    The location of disk group data file extents
    A redo log that records information about atomically changing metadata blocks
    Oracle ADVM volume information

PVID也存放于磁盘头部，如果对ASMDISK生成PVID，将覆盖元数据，启动时候会报错：

ORA-15063 "diskgroup \"%s\" lacks quorum of %s PST disks; %s found"
or
ORA-15063: ASM discovered an insufficient number of disks for diskgroup s%
ORA-15040: diskgroup is incomplete
ORA-15042: ASM disk "%" is missing

ASM磁盘不需要PVID。如果你的ASMDISK已经有PVID了，怎么将PVID安全地从磁盘头部除去呢？看以下文章：

In this Document

Goal

Solution

References

APPLIES TO:

Oracle Database - Enterprise Edition - Version 10.1.0.2 to 11.2.0.2 [Release 10.1 to 11.2]
IBM AIX on POWER Systems (64-bit)
IBM AIX Based Systems (64-bit)

GOAL

You have created a diskgroup with disks having PVID and the diskgroup is in use. There is no diskgroup metadata corruption reported yet. You now know that ASM Disk should not have PVID as alerted in MetaLink Note 353761.1

This note will give the steps to clear the PVID of these ASM Disks.

SOLUTION

When the PVID is set to a disk in a volume group, the PVID is stored in two locations. In Physical disk header ( within first 4K )and in AIX's system object database, called ODM ( Object Data Manager ).

PVID记录于两个位置1）磁盘头部4K；2）ODM库中

When the diskgroup is created, the disk header information of PVID is overwritten. However, with reboot the OS, from ODM, AIX might try to restore the PVID information onto the disk header,
there by destroying the ASM metadata.
创建asmdisk的时候会将PV磁盘头部的4K覆盖，但ODM库中依然保留着PVID信息，如果系统重启，AIX很可能会将PVID重新写入磁盘头部，致使ASM元数据损坏，导致数据库无法启动。

可以通过以下两种方法将已有ASMDISK的PVID去除：

If the ASM disk header Metadata has not been over written by PVID from ODM ( before a reboot ), then you can follow the following steps to update the ODM not to have PVID for the disks:

1] Do not reboot any node.

1.1] Drop one disk at a time from the diskgroup.

1.2] Clear the PVID of the dropped disk

# chdev -l hdisk5 -a pv=clear

Run this on ALL the nodes in case of RAC.

1.3] Check the disk does not have the PVID from ALL the nodes

# lspv

1.4] Add the disk back to the diskgroup

1.5] Do this for all the disks having PVID in the diskgroup, one by one. Take care that the rebalance is complete from the drop/add disk command before going for the next disk.

OR

2] This needs downtime:

2.1] Take 'dd' backup of the disk headers

# dd if=/dev/hdisk5 of=/tmp/d5.txt bs=1024 count=1024

2.2] Shutdown ASM instance ( on ALL the nodes in RAC setup ).

2.3] Clear the PVID

# chdev -l hdisk5 -a pv=clear

Run this on ALL the nodes in case of RAC.

2.4] Check the disk does not have the PVID from ALL the nodes

# lspv

2.5] Start the ASM Instance(s) and mount the diskgroup on ALL the nodes

WARNING:
Point-2 commands overrides the content of the disk header and so could be destructive if not correctly used. If you have any doubt, raise an SR with Oracle Support before any action.