/dev/disk/by-id/ata-CT500MX500SSD1_2045E4____4A
spare drive. will be used as a temporary boot drive.
/dev/disk/by-id/ata-CT500MX500SSD1_1934E2____65
rpool mirror vdev child. this drive will be taken out of the mirror to create a new rpool.
/dev/disk/by-id/ata-CT500MX500SSD1_2045E4____6C
rpool mirror vdev child, this drive will be the rollback if something goes wrong. Eventually it will be attached to the new rpool.