Storage Tiers and Storage Profiles

For all of the predefined Storage Profiles, the most preferred Storage Class and the RAID level always correspond to a valid storage tier.

For any Storage Domain, seven different types of storage tiers are possible for holding auto-tiered LUNs. The following table summarizes the possible storage tiers in a Storage Domain:

Table 1 Possible storage tiers in a Storage Domain
	Storage tier
Storage Class	Tier 1	Tier 2
Capacity HDD	RAID 6	Not available
Capacity SSD	RAID 5	RAID 10
Performance HDD	RAID 5	RAID 10
Performance SSD	RAID 5	RAID 10

In any given Storage Domain, however, only some of those tiers are present.

When creating or modifying an auto-tiered LUN, if you use a Storage Profile to define the QoS characteristics of the LUN, the system determines the starting storage tier for the LUN by evaluating the desired Storage Classes and the RAID level using the following process:

First, from the desired Storage Classes, the system selects the best Storage Class that is present in the Storage Domain.
If none of the desired Storage Classes are present, the system returns an error.
Note: This condition can only occur for custom storage profiles.
Using that Storage Class, the system changes the RAID level from RAID 5 to RAID 6 or from RAID 6 to RAID 5, depending on whether the change is necessary to match one of the tiers.