Automatic Storage Management (ASM) - Features,Properties - Oracle Control Files

Q.  Which of the following statements are true about Automatic Storage Management (ASM)?
- Published on 04 Aug 15

a. ASM provides mirroring on file by file basis
b. ASM provides automatic load balancing across all ASM disks
c. ASM supports the Oracle database and operating system files
d. ASM can be used to store trace files, alert log files, and the server parameter file (SPFILE)
e. Both A & B

ANSWER: Both A & B
 

    Discussion

  • Nirja Shah   -Posted on 28 Aug 15
    - ASM is a volume manager and a file system for Oracle database files that supports single-instance Oracle Database and Oracle Real Application Clusters (Oracle RAC) configurations.
    - ASM is Oracle's recommended storage management solution that provides an alternative to conventional volume managers, file systems, and raw devices.

    - ASM provides mirroring on file by file basis - Mirroring is the simplest way to gain data redundancy to safeguard data against disk failure.
    - In mirroring, two or more (minimum of three in LVM) disks or partitions are combined and identical data is written to each device.
    - The space available is only as large as the smallest device in the mirror.
    - Some implementations of mirroring offer increased read performance, but write performance is typically similar to traditional disk performance.
    - What mirroring does offer is the ability to keep running or recover more quickly as a redundant copy of the data is kept online and up-to-date.

    - ASM provides automatic load balancing across all ASM disks - Oracle has been promoting the concept of SAME.
    - Stripe and Mirror Everything which aimed at using the full I/O capacity of the all disks. Many database users have implemented SAME sets, each of about 4 mirrored disk pairs.
    - ASM takes an additional step in balancing I/O activity.
    - Rebalancing distributes file data evenly across all the disks of the ASM Disk Group.
    - ASM automatically rebalances a disk group whenever disks are added or dropped.
    - ASM ensures that a file is evenly spread across all disks in a disk group when the file is allocated, so rebalancing is not required except when the storage configuration changes.
    - With the I/O balanced whenever files are allocated and whenever the storage configuration changes, there is no need to search for hot spots in a disk group and manually move data to restore a balanced I/O load.
    - It also allows the addition of disks online.
    - There are extra background processes that conduct the rebalancing activity in a non-intrusive way.
    - Thus, ASM makes manual load balancing unnecessary because the dynamic rebalancing overcomes the major drawback of SAME.
    - When new disks are added to a disk group, rebalancing happens automatically without an outage.

    - The other two statements which are not true about ASM are:
    - ASM supports the Oracle database and operating system files
    - ASM can be used to store trace files, alert log files, and the server parameter file (SPFILE)

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