Developers Guide

20 Understanding RAID with Dell SC Series Storage | 3104-CD-DS
Snapshots prevent writes to data and then Data Progression moves the data to other RAID levels and tiers.
Figure 8 is an example of Data Progression for volumes using the recommended storage profile in a typical
two-tier environment.
Data Progression in a two-tier configuration
For volumes using the recommended storage profile in a three-tier configuration, Data Progression moves
data to each tier as illustrated in Figure 9.
Data progression in a three-tier configuration
5.4 Capacity within tiers
Statistically, only about 20 to 30 percent of user data is actively serving the needs of the applications, while 70
to 80 percent is less active. For capacity-planning purposes, assume that 20 to 30 percent of the total
capacity will be directed to Tier 1 disks and 70 to 80 percent can be accommodated by the other tiers of disks.
Since the data movement is dynamic, visibility to the actual RAID-level allocations is best observed by the
Dell Storage Manager Client or Enterprise Manager.