Updating cios wii
You can use a FAT32 SD/SDHC card for that purpose and set your USB hard drive as NTFS or Ext partition format.You can of course create multiple partitions format on your HDD if you want to separate partitions for Wii Homebrew, Wii games or your computer's data. If you want more informations between each format, you can read this.
will later allow you to specify a different IOS slot if you want to use different features (they will be detailed in other pages of this guides).
It has no other purpose than speeding the launching delay of the loader.