Oracle Automatic Storage Management

Oracle Automatic Storage Management (Oracle ASM) provides a vertically integrated file system and volume manager directly in the Oracle AI Database kernel.

This design provides several benefits, resulting in:

• Significantly less work to provision database storage

• Higher level of availability

• Elimination of the expense, installation, and maintenance of specialized storage products

• Unique capabilities for database applications

For optimal performance, Oracle ASM spreads files across all available storage. To protect against data loss, Oracle ASM extends the concept of SAME (stripe and mirror everything) and adds more flexibility because it can mirror at the database file level rather than at the entire disk level.

More important, Oracle ASM simplifies the processes of setting up mirroring, adding disks, and removing disks. Instead of managing hundreds or possibly thousands of files (as in a large data warehouse), database administrators using Oracle ASM create and administer a larger-grained object called a disk group. The disk group identifies the set of disks that are managed as a logical unit. Automation of file naming and placement of the underlying database files save administrators time and ensure adherence to standard best practices.

The Oracle ASM native mirroring mechanism (two-way or three-way) protects against storage failures. With Oracle ASM mirroring, you can provide an additional level of data protection with the use of failure groups. A failure group is a set of disks sharing a common resource (disk controller or an entire disk array) whose failure can be tolerated. After it is defined, an Oracle ASM failure group intelligently places redundant copies of the data in separate failure groups. This ensures that the data is available and transparently protected against the failure of any component in the storage subsystem.

By using Oracle ASM, you can:

• Mirror and stripe across drives and storage arrays.

• Automatically remirror from a failed drive to remaining drives.

• Automatically rebalance stored data when disks are added or removed while the database remains online.

• Support Oracle database files and non-database files using Oracle Advanced Cluster File System (Oracle ACFS).

• Allow for operational simplicity in managing database storage.

• Manage the Oracle Cluster Registry (OCR) and voting disks.

• Provide preferred read capability on disks that are local to the instance, which gives better performance for an extended cluster.

• Support very large databases.

• Support Oracle ASM rolling upgrades.

• Improve availability and reliability using the Oracle ASM disk scrubbing process to find and repair logical data corruptions using mirror disks.

• Support finer granularity in tuning and security.

• Provide fast repair after a temporary disk failure through Oracle ASM Fast Mirror Resync and automatic repair of block corruptions if a good copy exists in one of the mirrors.

• Provide disaster recovery capability for the file system by enabling replication of Oracle ACFS across the network to a remote site.

• Patch the Oracle ASM instance without impacting the clients that are being serviced using Oracle Flex ASM. A database instance can be directed to access Oracle ASM metadata from another location while the current Oracle ASM instance it is connected to is taken offline for planned maintenance.

• Monitor and manage the speed and status of Oracle ASM Disk Resync and Rebalance operations.

• Bring online multiple disks simultaneously and manage performance better by controlling resync parallelism using the Oracle ASM Resync Power Limit. Recover faster after a cell or disk failure, and the instance doing the resync is failing; this is made possible by using a Disk Resync Checkpoint which enables a resync to resume from where it was interrupted or stopped instead of starting from the beginning.

• Automatically connect database instances to another Oracle ASM instance using Oracle Flex ASM. The local database instance can still access the required metadata and data if an Oracle ASM instance fails due to an unplanned outage.

• Use flex diskgroups to prioritize high availability benefits across multiple databases all using the same diskgroup. Some of the key HA benefits are file extent redundancy, rebalance power limit, and rebalance priority. With flex diskgroups, you can set different values for the above features for different databases, resulting in prioritization across multiple databases within one diskgroup.

• Use flex diskgroups to implement quoto_groups across multiple databases sharing one diskgroup which helps in space management and protection.

• Use flex diskgroups to create point-in-time database clones using the ASM split mirror feature.

• Use preferred reads with stretch clusters to improve performance by affinitizing reads to a site. See Also: Oracle Automatic Storage Management Administrator’s Guide