In this paper we establish an improved outer bound on thestorage-repair-bandwidth tradeoff of regenerating codes under exact repair. Theresult shows that in particular, it is not possible to construct exact-repairregenerating codes that asymptotically achieve the tradeoff that holds forfunctional repair. While this had been shown earlier by Tian for the specialcase of $[n,k,d]=[4,3,3]$ the present result holds for general $[n,k,d]$. Thenew outer bound is obtained by building on the framework established earlier byShah et al.
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