Quality of Service (QoS), in general, defines a set of attributes for a logical volume that affects how the volume utilizes storage and the priority that the Oracle FS System gives to the I/O requests that target the volume.
The administrator creates a regular QoS volume by selecting the Single tier option in the GUI. Such a volume is sometimes referred to as a single-tiered volume.
The administrator creates a QoS Plus volume by selecting the Auto-tier option in the GUI. Such a volume is sometimes referred to as an auto-tiered volume.
The preferred type of storage media on which to place the user data initially. For QoS Plus volumes, the Storage Class and the RAID level of a volume determine the initial placement of the data.
Subsequently, the data usage statistics determine whether the data is migrated to another storage tier. Infrequently used data is moved to more cost-effective but lower-performance storage, while frequently used data is moved to a storage tier that has better performance characteristics.
A relative attribute that the system uses to set the importance and the treatment of logical volumes. A volume with a higher priority than another volume receives precedence in the handling of access requests. A higher priority also allows a larger share of typically finite resources, such as the storage tiers and the system cache.
Because the priority setting is relative, setting priorities to all low values or to all high values has the same effect, which nullifies the opportunity to distinguish between the service levels of volumes.
The type of data protection and the degree of data protection from drive failures. The type of protection influences the performance characteristics of the volume. The degree of protection determines the number of failures that can occur in a RAID group before having to restore the data from a backup of some kind.
The degree to which the storage system anticipates continuing read requests beyond an outstanding request. Correct anticipation greatly improves performance, while incorrect anticipation can waste system resources. By specifying a read-ahead policy, the administrator can provide an effective hint to the system to get the desired results of reading additional data blocks.
The level of redundancy (single or double)
The predominant access method (random, sequential, or a mix of the two access methods)
The predominant type of I/O request (read, write, or a mix of the two request types)
You can access the basic view of QoS by selecting a custom Storage Profile for the volume.