Oracle 11g R2 ASM:了解 Oracle ASM 基本概念
Jun 07, 2016 pm 03:02 PMAbout Oracle ASM Instances About Oracle ASM Disk Groups About Mirroring and Failure Groups About Oracle ASM Disks About Oracle ASM Files About Oracle ASM Instances Oracle ASM 實例基于和 Oracle Database 實例相同的技術(shù)構(gòu)建。Oracle ASM instan
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About Oracle ASM Instances
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About Oracle ASM Disk Groups
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About Mirroring and Failure Groups
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About Oracle ASM Disks
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About Oracle ASM Files
About Oracle ASM Instances
About Oracle ASM Disk Groups
About Mirroring and Failure Groups
About Oracle ASM Disks
About Oracle ASM Files
About Oracle ASM Instances
Oracle ASM 實例基于和 Oracle Database 實例相同的技術(shù)構(gòu)建。Oracle ASM instance 具有類似于 Oracle 數(shù)據(jù)庫實例的 System Global Area (SGA) 和后臺進程。但是,Oracle ASM 執(zhí)行的任務(wù)比數(shù)據(jù)庫實例要少, Oracle ASM SGA 要比數(shù)據(jù)庫實例的 SGA 小很多。此外,Oracle ASM 對服務(wù)器的性能影響非常小。Oracle ASM 實例負責 mount 磁盤組,使 Oracle ASM 文件對數(shù)據(jù)庫實例可用;Oracle ASM 實例不會 mount 數(shù)據(jù)庫。
Oracle ASM 安裝在 Oracle Grid Infrastructure home 中,而 Oracle Database 則安裝在單獨的 Oracle home 中。Oracle ASM 和數(shù)據(jù)庫實例都需要共享訪問磁盤組中的磁盤。 Oracle ASM 實例負責管理磁盤組的元數(shù)據(jù),為數(shù)據(jù)庫實例提供文件的布局信息。
Oracle ASM 使用 Oracle ASM 元數(shù)據(jù)來控制磁盤組。Oracle ASM 元數(shù)據(jù)位于磁盤組中,包含如下信息:
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磁盤和所屬磁盤組的對應(yīng)關(guān)系
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磁盤組上可用空間大小
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磁盤組上文件的文件名
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磁盤組數(shù)據(jù)文件的?extent?的位置
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記錄有關(guān)自動更改元數(shù)據(jù)塊的信息的 redo log
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Oracle ADVM 卷信息
Oracle ASM 可以通過 Oracle Clusterware 軟件實現(xiàn)集群化;每個集群節(jié)點一個 Oracle ASM 實例。如果同一個節(jié)點上存在多個同步的數(shù)據(jù)庫實例,則這些數(shù)據(jù)庫實例共用該節(jié)點上的一個 Oracle ASM 實例。
如果一個節(jié)點上的 Oracle ASM 實例失敗,則該節(jié)點上的所有數(shù)據(jù)庫實例也會失敗。與文件系統(tǒng)驅(qū)動器不一樣,一個 Oracle ASM 實例失敗不需要重啟操作系統(tǒng)。在 Oracle RAC 環(huán)境中,幸存節(jié)點上的 Oracle ASM 實例和數(shù)據(jù)庫實例會自動從失敗節(jié)點上的 Oracle ASM 實例進行恢復(fù)。
圖 1-1 顯示的是一個單節(jié)點 Oracle ASM 實例服務(wù)于多個數(shù)據(jù)庫實例的配置。Oracle ASM 實例負責管理元數(shù)據(jù),并未 Oracle ASM 文件提供空間分配。當數(shù)據(jù)庫實例創(chuàng)建或打開一個 Oracle ASM 文件時,數(shù)據(jù)庫實例首先會向 Oracle ASM 實例發(fā)出相應(yīng)請求。然后,Oracle ASM 會作出響應(yīng),為數(shù)據(jù)庫實例提供文件的 extent 位圖信息。
在圖?1-1?中有兩個磁盤組:一個磁盤組有4塊盤,另一個有2塊盤。數(shù)據(jù)庫對這兩個磁盤組都可以訪問。圖 1-1?顯示只需一個 Oracle ASM 實例便可為多個數(shù)據(jù)庫實例提供服務(wù)的配置。
Figure 1-1 Oracle ASM for Single-Instance Oracle Databases

圖 1-2?顯示的是 Oracle RAC 環(huán)境中的一個 Oracle ASM 集群,其中 Oracle ASM 提供了一個集群化的存儲池。每個節(jié)點一個 Oracle ASM 實例,集群中的多個 Oracle RAC 數(shù)據(jù)庫或單實例數(shù)據(jù)庫提供服務(wù)。所有數(shù)據(jù)庫都整合起來,共用兩個 Oracle ASM 磁盤組。
Figure 1-2 Oracle ASM Cluster Configuration with Oracle RAC

如??圖 1-3?所示,一個集群化存儲池可以被多個單實例 Oracle 數(shù)據(jù)庫所共用。在這種情況下,多個數(shù)據(jù)庫共享共用的磁盤組。共享 Oracle ASM 存儲池可以通過 Oracle Clusterware 實現(xiàn)。需要注意的是,在這類環(huán)境中不需要獲得 Oracle RAC license。
無論您是否要在節(jié)點上安裝 Oracle RAC,要在多個節(jié)點上共享磁盤組,必須在要共享的所有節(jié)點上安裝 Oracle Clusterware。單獨節(jié)點上的 Oracle ASM 實例不需要成為 Oracle ASM 集群的一部分。但是,如果該 Oracle ASM 實例不屬于某個 Oracle ASM 集群,則節(jié)點之間就無法彼此進行通信。不屬于一個 Oracle ASM 集群的多個節(jié)點無法共享 Oracle ASM 磁盤組。
Figure 1-3 Oracle ASM Cluster with Single-Instance Oracle Databases


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