Arch Linux

There is an issue (non-distro specific), which mainly applies to hard disks in notebooks and laptops (suspend to disk or shutdown). It appears to apply to Kernel 2.6.17 up to 2.6.21. (The regular 2.6.21.3-1 kernel as well as Suspend2 and ck variants are also affected).

There's a discussion here about it.
http://article.gmane.org/gmane.linux.scsi/30489
http://article.gmane.org/gmane.linux.ide/17392
http://linux-ata.org/shutdown.html

The problem is discussed here.
linux-kernel@vger.kernel.org/msg157749.html"> http://www.mail-archive.com/linux-kernel@vger.kernel.org/msg157749.html

And in Ubuntu buglist (where a temporary workaround is mentioned)
https://bugs.launchpad.net/ubuntu/+source/linux-source-2.6.17/+bug/67810

The issue has also been discussed in the Arch Linux forums.

Harddisk making a noise on shutdown
http://bbs.archlinux.org/viewtopic.php?pid=249653

The kernel bug tracker about the issue.
http://bugzilla.kernel.org/show_bug.cgi?id=7838
(This also has the patch).

A fix appears to be applied in Kernel release 2.6.22rc1.