请问mac分析数据中massstorage.external_drive_attributes表示什么意思？

com.apple.message.domain: com.apple.massstorage.external_drive_attributes
com.apple.message.__source__: SPI
com.apple.message.external_drive_present: 0
com.apple.message.external_fire_wire_present: 0
com.apple.message.external_sd_card_present: 0
com.apple.message.external_thunderbolt_present: 0
com.apple.message.external_usb_present: 0
com.apple.message.num_external_drives: 0
SenderMachUUID: B30950E3-5F8A-32F7-8589-E4C67701EC28