Oracle ASM

Question 1

What is ASM in Oracle?

Answer 1

ASM is a storage volume manager designed to manage Oracle database files. It simplifies and automates volume and file management. It also increases storage utilization, uptime, and agility.

Question 2

Advantages of ASM

Answer 2

• Striping: It spreads data evenly across all disks in a disk group to optimize performance and utilization.
• Mirroring: It can increase availability by optionally mirroring any file.
• Allows the removal or addition of disks from the disk storage system while the DB is operating.
• Reduces administration tasks by enabling files stored in ASM disk groups to be Oracle managed files.

Question 3

What are some characteristics of an ASM instance?

Answer 3

• Has SGA and background processes similar to Oracle but way smaller.
• Mount disk groups to make ASM files available to DB instances; they do not mount databases.

Question 4

What are the ASM initialization parameters?

Answer 4

• INSTANCE_TYPE
• DB_UNIQUE_NAME
• ASM_POWER_LIMIT: max power for rebalancing operation on an ASM instance.
• ASM_DISKGROUPS: list of disk groups that should be mounted by an ASM instance during startup.
• ASM_DISKSTRING: specifies a value that can be used to limit the disks considered for discovery.

Question 5

What is ASM rebalancing?

Answer 5

The main objective of the oracle ASM rebalance operation is to always provide an even distribution of the file extents and space usage across all disks in the disk group. Any change in the storage configuration will trigger it.

Question 6

What is RAID 0?

Answer 6

Consists of one or more logical volumes striped across two or more physical volumes.

Question 7

What is RAID 1?

Answer 7

Consists of one or more logical volumes mirrored across two or more disks.

Question 8

What is RAID 5?

Answer 8

0+1. Logical volume is cut across multiple physical volumes so concurrent read and writes are possible.

Question 9

What are types of redundancy?

Answer 9

• Normal: single mirror.
• High: creates three copies of every allocation unit thus requiring a minimum of three disks.
• External: no mirroring at all; assumption is that there is an underlying LVM that is doing whatever level of RAID is deemed appropriate.

Question 10

What is the difference between mirroring and striping in RAID?

Answer 10

• Striping divides data in one disk across various drives. This provides the greatest performance and efficiency. Smaller the stripes, faster the array.
• Mirroring is when data on one drive is duplicated on another array. This creates redundancy and reduces the chances for emergency RAID recovery.