Definition

Erasure coding: overhead and repair

Any k of the n = k + m chunks can rebuild the object.

overhead = \frac{n}{k} = \frac{k + m}{k}, repair read = k \times lost

Worked examples, recomputed

Every number the mechanisms quote for this relationship is recomputed from it, so none of them disagrees with it.

Each mechanism states it in its own names. The general symbol each name stands for is shown with it.

Persistence & Durability
When a system says "yes, your data is safe", what exactly has it promised, and what did it have to do to keep that promise?
$Storage overhead = n / k$
Read it in place →