ask for asm with redundancy and failure group options

xrootman

Oracle ASM Failure Groups

Failure groups are used to store mirror copies of data. When Oracle ASM allocates an extent for a normal redundancy file, Oracle ASM allocates a primary copy and a secondary copy. Oracle ASM chooses the disk on which to store the secondary copy so that it is in a different failure group than the primary copy. Each copy is on a disk in a different failure group so that the simultaneous failure of all disks in a failure group does not result in data loss.

A failure group is a subset of the disks in a disk group, which could fail at the same time because they share hardware. The failure of common hardware must be tolerated. Four drives that are in a single removable tray of a large JBOD (Just a Bunch of Disks) array should be in the same failure group because the tray could be removed making all four drives fail at the same time. Drives in the same cabinet could be in multiple failure groups if the cabinet has redundant power and cooling so that it is not necessary to protect against failure of the entire cabinet. However, Oracle ASM mirroring is not intended to protect against a fire in the computer room that destroys the entire cabinet.

There are always failure groups even if they are not explicitly created. If you do not specify a failure group for a disk, then Oracle automatically creates a new failure group containing just that disk, except for disk groups containing disks on Oracle Exadata cells.

A normal redundancy disk group must contain at least two failure groups. A high redundancy disk group must contain at least three failure groups. However, Oracle recommends using several failure groups. A small number of failure groups, or failure groups of uneven capacity, can create allocation problems that prevent full use of all of the available storage.

Failure groups can be specified as regular or quorum failure groups. For information about quorum failure groups, see "Oracle Cluster Registry and Voting Files in Oracle ASM Disk Groups".

这上官档原文，1.看完了但是我还是没有很明确的了解fail groups到底有什么作用？2.A failure group is a subset of the disks in a disk group, which could fail at the same time because they share hardware. 这里意味着是否是只能在一个存储上？3.冗余与file groups的区别？ 请兄弟们帮忙详解一下。

xrootman

第一问和第三问可以忽略了，重点第二问.

Maclean Liu(刘相兵

2.A failure group is a subset of the disks in a disk group, which could fail at the same time because they share hardware. 这里意味着是否是只能在一个存储上？

不是


好比 你有2个disk controller 或者干脆有2个存储

那么你完全有必要 为这个2个 controller/storage 分别建立一个failgroup， 但一个存储彻底失败时 ，当一个failgroup彻底失败时 保证diskgroup仍可用

Maclean Liu(刘相兵

3.冗余与file groups的区别？ 请兄弟们帮忙详解一下。

冗余只有3个级别： high 、normal、external

但是你可以创建超过3个failgroup，例如使用 high redundancy ，而你建立了4个failgroup，则通俗地说一个 1份数据仍保留三份，会在4个failgroup中选择3个存放 数据副本。

willing_ox

http://www.dbform.com/html/2006/218.html

这篇文章写的挺清楚。

xrootman

刘大多谢了，因我这机器配置不行所以没有验证，不过区别官档的意思区别还是在于extent与磁盘镜像的区别