Storage Tiers

A storage tier is a collection of blocks of contiguous storage, all of which have the same RAID level. This collection is spread across one or more drive groups within a given Storage Domain. Storage tiers are used by administrators and by the Oracle FS System to provision logical volumes.

When an administrator initially creates a LUN, the administrator defines a number of QoS properties for the volume, including the initial Storage Class for the volume. If the LUN uses QoS Plus, the Oracle FS System creates two storage tiers in the Storage Domain that the administrator selects for the volume:

For capacity HDDs, the system creates a RAID 6 storage tier, which implements double redundancy, and a RAID 10 storage tier, which implements mirroring.
For all other drives, the system creates a RAID 5 storage tier, which implements single redundancy, and a RAID 10 storage tier as well.

Note: The RAID level of the storage tiers depends on the Storage Class that is selected for the LUN.

The storage tier on which the system places the LUN depends on the Storage Class and on the redundancy level (single parity, double parity, or mirroring) that the administrator selects for the volume.

Note: For filesystems, an Oracle FS System uses two types of storage tiers: data tiers and metadata tiers. A filesystem data tier contains user data. A filesystem metadata tier contains system-level data that describe the filesystem and the user data that it contains.