我能够从外部 USB 硬盘启动和运行命令；有问题的消息出现约 45 秒，然后启动继续。GRUB2 安装在内部硬盘上。When choosing to boot directly to /dev/sdb the message doesn't appear, however boot time is about the same as booting to internal HDD.
/dev/sdb:
Timing cached reads: 1018 MB in 2.00 seconds = 508.97 MB/sec
Timing buffered disk reads: 80 MB in 3.03 seconds = 26.37 MB/sec
pfeiffep@de:~$ sudo hdparm -i /dev/sdb
/dev/sdb:
SG_IO: bad/missing sense data, sb[]: 70 00 05 00 00 00 00 10 00 00 00 00 20 00 00 00 00 …