It is well known that it is possible to construct regenerating codes with exact repair that operate at the minimum storage regeneration (MSR) and minimum bandwidth regenerating (MBR) endpoints of the storage-repair bandwidth tradeoff. It has also been known for some time, that it is not possible to construct exact-repair codes that operate exactly at an interior point, except possibly, in a small region adjacent to the MSR point. There have been three recent results relating to code constructions for the interior points. In the first, a normalized version of the classical storage-repair bandwidth tradeoff is introduced. This shows that when measured against practical metrics such as storage overhead and average repair bandwidth per unit time and unit data symbol stored, interior-point constructions are of equal importance as constructions for MSR and MBR points. A second major result uses an information-theory inequality prover to establish that it is not possible in general, to construct codes that achieve the interior points even asymptotically. The third result presents a construction for regenerating codes that does better than space-sharing, compares well with codes for MSR and MBR points when viewed in the normalized tradeoff framework, and which is capable of achieving a single interior point. An overview of these results is presented here.
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