Dell PowerVault ME4 Series Storage System Administrator’s Guide

Volume tier affinity strategies

Volume tier affinity acts as a guide to the system on where to place data for a given volume in the available tiers.

The standard strategy is to prefer the highest spinning disk tiers for new sequential writes and the highest tier available (including SSD) for new random writes. As the host application accesses the data, it is moved to the most appropriate tier based on demand. Frequently accessed data is promoted up towards the highest performance tier and infrequently accessed data is demoted to the lower spinning disk-based tiers. The standard strategy is followed for data on volumes set to No Affinity.

For data on volumes set to the Performance affinity, the standard strategy is followed for all new writes. However, subsequent access to that data has a lower threshold for promotion upwards. The lower threshold makes it more likely for that data to be available on the higher performance tiers. Preferential treatment is provided to frequently accessed data that has performance affinity at the SSD tier. Archive or no affinity data is demoted out of the SSD tier to make room for data with an affinity of Performance. The Performance affinity is useful for volume data that you want to ensure has priority treatment for promotion to and retention in your highest performance tier.

For volumes that are set to the Archive affinity, all new writes are initially placed in the archive tier. If no space is available in the archive tier, new writes are placed on the next higher tier available. Subsequent access to that data enables for its promotion to the performance tiers as it is accessed more often. However, the data has a lower threshold for demotion. The data is moved out of the highest performance SSD tier when there is a need to promote frequently accessed data up from a lower tier.