Tahoe-LAFS performance leaves a lot to be desired, for various reasons, but the erasure-coding levels (i.e. the degree of distribution of each file via "RAID"-like math) aren't necessarily the most important component. Brian Warner did some thorough benchmarks using dedicated servers on a LAN, and specifically look at how increasing the number of shares ("K") affected throughput:
The different colors of the samples there are for three different settings of how many shares the file was erasure-coded (RAIDed) into: 3, 30, or 60 shares. This type of file ("MDMF" type) seems to go about as fast at any of those three levels of distribution, but this older and more common type -- https://tahoe-lafs.org/trac/tahoe-lafs/attachment/wiki/Perfo... -- ("CHK" type, which is for immutable files) performs much worse for larger levels of distribution. There's probably just some dumb bug which causes this slowdown. This page has some ideas as to what's causing it: https://tahoe-lafs.org/trac/tahoe-lafs/wiki/Performance/Sep2...
https://tahoe-lafs.org/trac/tahoe-lafs/attachment/wiki/Perfo...
The different colors of the samples there are for three different settings of how many shares the file was erasure-coded (RAIDed) into: 3, 30, or 60 shares. This type of file ("MDMF" type) seems to go about as fast at any of those three levels of distribution, but this older and more common type -- https://tahoe-lafs.org/trac/tahoe-lafs/attachment/wiki/Perfo... -- ("CHK" type, which is for immutable files) performs much worse for larger levels of distribution. There's probably just some dumb bug which causes this slowdown. This page has some ideas as to what's causing it: https://tahoe-lafs.org/trac/tahoe-lafs/wiki/Performance/Sep2...