extract from /tmp/recovery.log

...
Partition Logs:
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/system | /dev/block/mmcblk0p66 | Size: 4339MB Used: 2129MB Free: 2209MB Backup Size: 2129MB
   Flags: Can_Be_Mounted Can_Be_Wiped Can_Be_Backed_Up Wipe_Available_in_GUI IsPresent
   Primary_Block_Device: /dev/block/mmcblk0p66
   Display_Name: System
   Storage_Name: System
   Backup_Path: /system
   Backup_Name: system
   Backup_Display_Name: System
   Storage_Path: /system
   Current_File_System: ext4
   Fstab_File_System: ext4
   Backup_Method: files

/system_image | /dev/block/mmcblk0p66 | Size: 4480MB
   Flags: Can_Be_Backed_Up IsPresent
   Primary_Block_Device: /dev/block/mmcblk0p66
   Display_Name: System Image
   Storage_Name: system_image
   Backup_Path: /system_image
   Backup_Name: system_image
   Backup_Display_Name: System Image
   Storage_Path: /system_image
   Current_File_System: emmc
   Fstab_File_System: emmc
   Backup_Method: dd
...