[Gen8 Android Development] axm6:
I tried something in init.rc in /:

mount ext4 /dev/block/mmcblk1p1 /mnt/sdcard
mount vfat /dev/block/mmcblk1p1 /mnt/sdcard
mount ext3 /dev/block/mmcblk0p2 /mnt/system
mount vfat /dev/block/mmcblk2p1 /mnt/sdcard/sdcard

And I tried to replace sdcard by storage, and it works

I also put that in vold.fstab:

# Mounts the first usable partition of the specified device
dev_mount emmc /mnt/storage 1 /dev/block/platform/mmci-omap-hs.1/mmcblk1
dev_mount emmc2 /mnt/storage/sdcard auto /dev/block/platform/mmci-omap-hs.0/mmcblk2
#dev_mount volume_external /mnt/sdcard/usb_host auto SDCARD=/class/block/sda
dev_mount volume_external /mnt/usb auto SDCARD=/dev/block/mmcblk2

But I think it's useless because, my storage is mounted at /mnt/sdcard

Edit:

Edit 2 :the build.prop:

# begin build properties
# autogenerated by buildinfo.sh
ro.build.id=IMM76L
ro.build.display.id=full_archosg8-userdebug 4.0.4 IMM76L eng.root.20130508.174735 test-keys
ro.build.version.incremental=eng.root.20130508.174735
ro.build.version.sdk=15
ro.build.version.codename=REL
ro.build.version.release=4.0.4
ro.build.date=mercredi 8 mai 2013, 17:50:59 (UTC+0200)
ro.build.date.utc=1368028259
ro.build.type=userdebug
ro.build.user=root
ro.build.host=bizcuite-laptop
ro.build.tags=test-keys
ro.product.model=Nexus 4
ro.product.brand=Android
ro.product.name=full_archosg8
ro.product.device=g8
ro.product.board=archos
ro.product.cpu.abi=armeabi-v7a
ro.product.cpu.abi2=armeabi
ro.product.manufacturer=archos
ro.product.locale.language=en
ro.product.locale.region=US
ro.wifi.channels=
ro.board.platform=omap3
# ro.build.product is obsolete; use ro.product.device
ro.build.product=g8
ro.sf.lcd_density=160
# Do not try to parse ro.build.description or .fingerprint
ro.build.description=full_archosg8-userdebug 4.0.4 IMM76L eng.root.20130508.174735 test-keys
ro.build.fingerprint=Android/full_archosg8/g8:4.0.4/IMM76L/eng.root.20130508.174735:userdebug/test-keys
ro.build.characteristics=tablet,nosdcard
ro.cm.device=g8
# end build properties

#
# ADDITIONAL_BUILD_PROPERTIES
#
keyguard.no_require_sim=true
ro.com.android.dateformat=MM-dd-yyyy
com.ti.omap_enhancement=true
wifi.interface=tiwlan0
net.dns1=8.8.8.8
net.dns2=8.8.4.4
qemu.hw.mainkeys=0
wifi.supplicant_scan_interval=180
ro.display.switch=1
ro.opengles.version=131072
persist.service.sv.enable=1
jpeg.libskiahw.encoder.enable=1
jpeg.libskiahw.decoder.enable=1
jpeg.libskiahw.decoder.thresh=350000
jpeg.libskiahw.encoder.thresh=0
persist.sys.strictmode.visual=0
persist.sys.strictmode.disable=1
hwui.render_dirty_regions=false
persist.sys.usb.config=mass_storage,adb
ro.ui.fullscreen=false
ro.kernel.android.checkjni=0
ro.carrier=wifi-only
view.touch_slop=8
view.minimum_fling_velocity=25
view.scroll_friction=0.008
ro.ril.disable.power.collapse=1
debug.performance.tuning=1
video.accelerate.hw=1
dalvik.vm.lockprof.threshold=150
dalvik.vm.verify_bytecode=false
ro.mot.hw.HAC=1
dalvik.vm.checkjni=false
dalvik.vm.verify-bytecode=false
ro.kernel.checkjni=0
dalvik.vm.execution-mode=int:jit
persist.sys.use_dithering=1
alsa.mixer.playback.master=default
alsa.mixer.capture.master=Analog
ro.setupwizard.enable_bypass=1
ro.telephony.default_network=0
dalvik.vm.heapstartsize=5m
dalvik.vm.heapgrowthlimit=48m
dalvik.vm.heapsize=256m
dalvik.vm.dexopt-flags=m=y
net.bt.name=Android
dalvik.vm.stack-trace-file=/data/anr/traces.txt