Centos - fstab - mount keeps changing
If your BIOS is detecting devices in a different order you can mount by label or by UUID. (You can see your /boot mount is already doing this.)
LABEL=filesystemlabel /mnt/directory type options
-or-
UUID=uuidhere /mnt/directory type options
You can get the UUID with the blkid command or the label with e2label. (Assuming ext2/ext3.) If it has no label, you can set it e2label also, or tune2fs.