Oracle Automatic Storage Management(Oracle ASM),Oracle ASM Cluster File System(Oracle ACFS),and Oracle ASM Dynamic Volume Manager(Oracle ADVM) are key components of storage management.
Recommended storage management solution
Oracle ASM is a volume management and a file system for Oracle Database files that supports single-instance Oracle Database and Oracle Real Application Clusters(Oracle RAC) configurations.
Oracle ASM uses disk groups to store data files.
The content of files that are stored in a disk group is evenly distributed to eliminate hot spots and a provide uniform performance across the disks.
Oracle ASM has easy to use management interfaces such as SQL*Plus,the Oracle ASM Command Line Utility (ASMCMD) command-line interface, and Oracle ASM Configuration Assistant(ASMCA).
Oracle ASM Instances
An Oracle ASM instance is built in on the same technology as an Oracle Database instance.
An Oracle ASM instance has a System Global Area(SGA) and background processes that are similar to those of Database.
Oracle ASM instances do not mount database.
Oracle ASM is installed in the Oracle Grid Infrastructure home before Oracle Database is installed in a separate Oracle home.
Oracle ASM Disk Groups 类似lvm Disk group components include disks, files, and allocation units.
Mirroring and Failure Groups
Redundancy levels
Normal for 2-way mirroring High for 3-way mirroring External hardware RAID
ASM Disks
Oracle ASM disks include: 1)a disk or partition from a storage array 2)entire disk or the partitions of a disk 3)logincal volumes 4)network-attached files(NFS)
ASM Allocation Units
Every Oracle ASM disk is divided into allocation units(AU).
A file extent consists of one or more allocation units.
An Oracle ASM file consists of one or more file extents.
Oracle ASM Files
Files that are stored in Oracle ASM disk groups are called Oracle ASM fils.
Oracle ASM file names begin with a plus sign(+) followed by a disk group name.
