  Locally repairable codes (LRCs) are error correcting codes used in distributed data storage. Besides a global level, they enable errors to be corrected locally, reducing the need for communication between storage nodes. There is a close connection between almost affine LRCs and matroid theory which can be utilized to construct good LRCs and derive bounds on their performance.   A generalized Singleton bound for linear LRCs with parameters $(n,k,d,r,\delta)$ was given in [N. Prakash et al., "Optimal Linear Codes with a Local-Error-Correction Property", IEEE Int. Symp. Inf. Theory]. In this paper, a LRC achieving this bound is called perfect. Results on the existence and nonexistence of linear perfect $(n,k,d,r,\delta)$-LRCs were given in [W. Song et al., "Optimal locally repairable codes", IEEE J. Sel. Areas Comm.]. Using matroid theory, these existence and nonexistence results were later strengthened in [T. Westerb\"ack et al., "On the Combinatorics of Locally Repairable Codes", Arxiv: 1501.00153], which also provided a general lower bound on the maximal achievable minimum distance $d_{\rm{max}}(n,k,r,\delta)$ that a linear LRC with parameters $(n,k,r,\delta)$ can have. This article expands the class of parameters $(n,k,d,r,\delta)$ for which there exist perfect linear LRCs and improves the lower bound for $d_{\rm{max}}(n,k,r,\delta)$. Further, this bound is proved to be optimal for the class of matroids that is used to derive the existence bounds of linear LRCs. 
Bounds on the Maximal Minimum Distance of Linear Locally Repairable   Codes