[HD2 Android NAND Development] Luz:
here is the partition log of TWRP (I just installed it)

I can see the 10Gb Fat32 and the 4.5Gb EXT4 : /

Partition Logs:

/cache | /dev/block/mtdblock4 | Size: 2MB Used: 0MB Free: 1MB Backup Size: 0MB

Flags: Can_Be_Wiped Can_Be_Backed_Up Wipe_During_Factory_Reset Wipe_Available_in_GUI Is_Present

Primary_Block_Device: /dev/block/mtdblock4

MTD_Dev: /dev/mtd/mtd4

Fstab_File_System: yaffs2

Current_File_System: yaffs2

Storage_Path: /cache

Backup_Path: /cache

Display_Name: Cache

Storage_Name: Cache

Backup_Name: cache

Backup_Display_Name: Cache

MTD_Name: cache

Backup_Method: files

/misc | /dev/block/mtdblock0 | Size: 1MB Used: 1MB Free: 0MB Backup Size: 1MB

Flags: Can_Be_Wiped Is_Present

Primary_Block_Device: /dev/block/mtdblock0

MTD_Dev: /dev/mtd/mtd0

Fstab_File_System: mtd

Current_File_System: mtd

Backup_Path: /misc

Display_Name: misc

Storage_Name: misc

Backup_Name: misc

Backup_Display_Name: misc

MTD_Name: misc

Backup_Method: flash_utils

/recovery | /dev/block/mtdblock1 | Size: 10MB Used: 10MB Free: 0MB Backup Size: 10MB

Flags: Can_Be_Wiped Can_Be_Backed_Up Is_Present

Primary_Block_Device: /dev/block/mtdblock1

MTD_Dev: /dev/mtd/mtd1

Fstab_File_System: mtd

Current_File_System: mtd

Backup_Path: /recovery

Display_Name: Recovery

Storage_Name: recovery

Backup_Name: recovery

Backup_Display_Name: Recovery

MTD_Name: recovery

Backup_Method: flash_utils

/sdcard | /dev/block/mmcblk0p1 | Size: 9989MB Used: 205MB Free: 9783MB Backup Size: 0MB

Flags: Can_Be_Wiped Can_Be_Backed_Up Wipe_Available_in_GUI Removable Is_Present Has_Android_Secure Is_Storage Is_Settings_Storage

Primary_Block_Device: /dev/block/mmcblk0p1

Fstab_File_System: vfat

Current_File_System: vfat

Symlink_Path: /sdcard/.android_secure

Symlink_Mount_Point: /and-sec

Alternate_Block_Device: /dev/block/mmcblk0

Storage_Path: /sdcard

Backup_Path: /and-sec

Display_Name: sdcard

Storage_Name: sdcard

Backup_Name: and-sec

Backup_Display_Name: Android Secure

Backup_Method: files

/data | /dev/block/mtdblock5 | Size: 52MB Used: 1MB Free: 51MB Backup Size: 1MB

Flags: Can_Be_Wiped Can_Be_Backed_Up Wipe_During_Factory_Reset Wipe_Available_in_GUI Is_Present Can_Be_Encrypted

Primary_Block_Device: /dev/block/mtdblock5

MTD_Dev: /dev/mtd/mtd5

Fstab_File_System: yaffs2

Current_File_System: yaffs2

Storage_Path: /data

Backup_Path: /data

Display_Name: Data

Storage_Name: Data

Backup_Name: data

Backup_Display_Name: Data

MTD_Name: userdata

Backup_Method: files

/boot | /dev/block/mtdblock2 | Size: 5MB Used: 0MB Free: 4MB Backup Size: 0MB

Flags: Can_Be_Wiped Can_Be_Backed_Up Wipe_Available_in_GUI Is_Present

Primary_Block_Device: /dev/block/mtdblock2

MTD_Dev: /dev/mtd/mtd2

Fstab_File_System: yaffs2

Current_File_System: yaffs2

Storage_Path: /boot

Backup_Path: /boot

Display_Name: Boot

Storage_Name: boot

Backup_Name: boot

Backup_Display_Name: Boot

MTD_Name: boot

Backup_Method: files

/system | /dev/block/mtdblock3 | Size: 350MB Used: 1MB Free: 348MB Backup Size: 1MB

Flags: Can_Be_Wiped Can_Be_Backed_Up Wipe_Available_in_GUI Is_Present

Primary_Block_Device: /dev/block/mtdblock3

MTD_Dev: /dev/mtd/mtd3

Fstab_File_System: yaffs2

Current_File_System: yaffs2

Storage_Path: /system

Backup_Path: /system

Display_Name: System

Storage_Name: System

Backup_Name: system

Backup_Display_Name: System

MTD_Name: system

Backup_Method: files

/sd-ext | /dev/block/mmcblk0p2 | Size: 4859MB Used: 73MB Dalvik-Cache: 21MB Free: 4785MB Backup Size: 73MB

Flags: Can_Be_Wiped Can_Be_Backed_Up Wipe_During_Factory_Reset Wipe_Available_in_GUI Removable Is_Present

Primary_Block_Device: /dev/block/mmcblk0p2

Fstab_File_System: auto

Current_File_System: ext4

Storage_Path: /sd-ext

Backup_Path: /sd-ext

Display_Name: SD-Ext

Storage_Name: SD-Ext

Backup_Name: sd-ext

Backup_Display_Name: SD-Ext

Backup_Method: files

/sdext2 | /---/-----/--------- | Size: 0MB Used: 0MB Free: 0MB Backup Size: 0MB

Flags:

Primary_Block_Device: /dev/block/mmcblk0p3

Fstab_File_System: auto

Current_File_System: auto

Edit : Ho and in the TWRP file browser, I can see a sd-ext folder and brows it.