je viens de débrancher le disque et je l'ai mis sur un autre port usb pour voir:
avec la commande (fdisk -l) j'obtient:
GPT PMBR size mismatch (239649 != 245759) will be corrected by w(rite).
Disk /dev/synoboot: 120 MiB, 125829120 bytes, 245760 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: 69CADB00-xxxxx
Device Start End Sectors Size Type
/dev/synoboot1 2048 67583 65536 32M EFI System
/dev/synoboot2 67584 239615 172032 84M Linux filesystem
Disk /dev/sdq: 9.1 TiB, 10000797794304 bytes, 19532808192 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: gpt
Disk identifier: 8F82D846-xxxx