In some examples, a controller for a storage system separate from a host system checks whether a storage cartridge in a storage system is associated with an indication set, in an electronic memory, during a configuration operation in the storage system to indicate write protection is enabled for the storage cartridge. In response to determining that the storage cartridge is associated with the indication, the controller triggers the write protection for the storage cartridge to prevent writing of data to the storage cartridge if the storage cartridge already contains previously written data.