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why does ax86u has only 47mb jffs when it has 256MB flash?

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2ig2ag

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Bash:
RT-AX86U-8D08# df -h
Filesystem                Size      Used Available Use% Mounted on
ubi:rootfs_ubifs         77.7M     75.7M      2.1M  97% /
devtmpfs                456.0M         0    456.0M   0% /dev
tmpfs                   456.1M    720.0K    455.4M   0% /var
tmpfs                   456.1M      1.1M    454.9M   0% /tmp/mnt
ubi1:data                 4.5M     64.0K      4.2M   1% /data
tmpfs                   456.1M      1.1M    454.9M   0% /tmp/mnt
tmpfs                   456.1M      1.1M    454.9M   0% /tmp
/dev/mtdblock9           47.0M     25.5M     21.5M  54% /jffs

The root has 77.7M and jffs has 47.0M. That's 124.7 MB in total. It's far from "256 MB Flash" in Asus's tech specs.
What gives?
 
The flash memory is used for more than the visible filesystems. But most of the "missing" space is used to hold a backup copy of the entire firmware image. So should the current firmware get corrupted it's possible to recover from the previous version.
 
96 MB for the first firmware partition.
96 MB for the second firmware partition
Some portions for bootloader, crashlog storage, system data, etc...
What's left (around 48 MB) is for JFFS.
 

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