# Locally Repairable Codes with Multiple $(r_{i}, \delta_{i})$-Localities

## TL;DR

This paper introduces a generalized class of locally repairable codes with multiple localities and failure tolerances, providing theoretical bounds and explicit constructions to improve repair efficiency and fault tolerance in distributed storage systems.

## Contribution

It generalizes ML-LRCs to multiple $(r_{i}, oldsymbol{\delta_{i}})$-localities, derives a Singleton-like bound, and constructs optimal codes with these properties.

## Key findings

- Derived a Singleton-like upper bound on minimum distance.
- Provided explicit constructions of optimal ML-LRCs.
- Extended constructions to multiple localities with different parameters.

## Abstract

In distributed storage systems, locally repairable codes (LRCs) are introduced to realize low disk I/O and repair cost. In order to tolerate multiple node failures, the LRCs with \emph{$(r, \delta)$-locality} are further proposed. Since hot data is not uncommon in a distributed storage system, both Zeh \emph{et al.} and Kadhe \emph{et al.} focus on the LRCs with \emph{multiple localities or unequal localities} (ML-LRCs) recently, which said that the localities among the code symbols can be different. ML-LRCs are attractive and useful in reducing repair cost for hot data. In this paper, we generalize the ML-LRCs to the $(r,\delta)$-locality case of multiple node failures, and define an LRC with multiple $(r_{i}, \delta_{i})_{i\in [s]}$ localities ($s\ge 2$), where $r_{1}\leq r_{2}\leq\dots\leq r_{s}$ and $\delta_{1}\geq\delta_{2}\geq\dots\geq\delta_{s}\geq2$. Such codes ensure that some hot data could be repaired more quickly and have better failure-tolerance in certain cases because of relatively smaller $r_{i}$ and larger $\delta_{i}$. Then, we derive a Singleton-like upper bound on the minimum distance for the proposed LRCs by employing the regenerating-set technique. Finally, we obtain a class of explicit and structured constructions of optimal ML-LRCs, and further extend them to the cases of multiple $(r_{i}, \delta)_{i\in [s]}$ localities.