  Consider the following fundamental question of distributed storage networks:
Given any arbitrary $(n,k,d)$ values, whether there exists an intelligent
helper selection scheme (assuming unlimited memory and computing power) that
can strictly improve the storage-bandwidth (S-B) tradeoff. Ahmad et al. 18'
answered this question by proving that for a subset of $(n,k,d)$ values, no
helper selection scheme can ever improve the S-B tradeoff, and for the
$(n,k,d)$ not in that subset, a new scheme called family helper selection (FHS)
can strictly improve the S-B tradeoff over a blind helper selection scheme.
Nonetheless, the analysis of FHS is done by a min-cut analysis with no actual
code construction.
  This work fills this gap between pure min-cut analysis and actual code
construction by pairing FHS with a new, generalized version of the existing
fractional repetition (FR) codes. Specifically, existing FR codes are
exact-repair codes that admit the highly-desirable repair-by-transfer property,
but its unique construction limits the application to a restricted set of
$(n,k,d)$ values. In contrast, our new construction, termed flexible fractional
repetition codes, can be applied to arbitrary $(n,k,d)$ while retaining most of
the practical benefits of FR codes, i.e., admitting small repair bandwidth,
being exact-repair, and being almost repairable-by-transfer.
