Reliability statement and assumptions

Independent failure of disk drives is the primary path to data loss. Concentrated Dispersal, while allowing multiple slices of the same object to exist in the same Slicestor, prevents multiple slices of the same object from ending up on the same disk, so long as the number of active disks within a Slicestor is greater than the number of pillars the store is responsible for. That is if: Disks_Per_Slicestor ≥ (IDA_Width / Physical_Width). All IDA configurations for Concentrated Dispersal systems enforce this constraint, and go beyond it by ensuring Slicestor devices have at least twice as many drives as pillars.

It is important to note that reliability will still decrease under a Concentrated Dispersal configuration, as non-independent disk failure events could impact several disks within a store.