Who don't you change the GRUB root volume to use a UUID? Then you won't ever worry about device numbering/naming again.
case:~# hdparm -tT /dev/sda /dev/sda: Timing cached reads: 852 MB in 2.00 seconds = 425.00 MB/sec HDIO_DRIVE_CMD(null) (wait for flush complete) failed: Inappropriate ioctl for device Timing buffered ...
Some results have been hidden because they may be inaccessible to you
Show inaccessible results