Dell PowerVault ME5 Series Administrator's Guide

About automated tiered storage

Automated Tiered Storage is a virtual storage feature that automatically moves data residing in one class of disks to a more appropriate class of disks based on data access patterns, with no manual configuration necessary.

• Frequently accessed data can move to disks with higher performance.
• Infrequently accessed data can move to disks with lower performance and lower costs.

Each virtual disk group, depending on the type of disks it uses, is automatically assigned to one of the following tiers:

• Performance – This highest tier uses SSDs, which provide the best performance but also the highest cost. For more information on SSDs, see About SSDs.
• Standard – This middle tier uses enterprise-class spinning SAS disks, which provide good performance with mid-level cost and capacity.
• Archive – This lowest tier uses midline spinning SAS disks, which provide the lowest performance with the lowest cost and highest capacity.

When the status of a disk group in the Performance Tier becomes critical (CRIT), the system will automatically drain data from that disk group to disk groups using spinning disks in other tiers providing that they can contain the data on the degraded disk group. This occurs because similar wear across the SSDs is likely, so more failures may be imminent.

If a system only has one class of disk, no tiering occurs. However, automated tiered storage rebalancing happens when adding or removing a disk group in a different tier.