/dev/sdawhile the old one was
/dev/sdb. So while installing grub, I assumed the following mapping:
However, when I rebooted, grub showed error 17. A quick look at Grub error collection shows that I had somehow got
root(hdX, Y)wrong. While talking about the issue on #gentoo, I found that hd0 is actually the drive the BIOS is set to boot from. So, my assumed mapping was incorrect and it turned out that hd0 was being mapped to 11tb hard drive. So, I went into the BIOS and changed it so that the correct mapping was followed.
P.S. To know more about grub read this article.