I have a WNDR3700v4 and a WRT1900ACS. Both supposedly have 128 MB Flash. Both show 24 MB total on the software tab of Luci, and when running df over ssh. Where has the remaining 104 MB of Flash gone, and how do I get to it? Will standard releases of LEDE/OpenWRT ever properly support these high-end routers, or have I been doing something wrong for the past several years where they are actually supported and I just installed the firmware incorrectly?
Shelby flash layout
So what is the point of losing half of the available space to apparently duplicate data? It can't be necessary given the smaller (8-16 MB) routers aren't set up that way...
That is the default made by Linksys. The alternative firmware partition provides a fallback in case the new firmware does not work.
Openwrt and LEDE simply keep the existing partition structure intact.
lede is simply preserving the partition layout decided by linksys/netgear in case you want to flash back to stock.
You can mount the unused partition and install packages there. Please search in the openwrt wiki.
But really - what is your use case? Just my experience - usually 16mb of flash got enough space for installing packages for most use cases. And generally you don't want to overload the router serving way too many purposes.
Please read this LEDE on WNDR3700v4 (available flash size)
there is a patch to safely use whole 128 MB on WNDR 3700v4. I compiled it myself and it's working great since i bought it