Lvm – Hard Drive chugging noise when moutning Logical Volume to file system

I have a server (Ubuntu 11.04) with a RAID 10 array (4 disks), and the RAID 10 array is partitioned as one big LVM. I have a logical volume on that which is 40GB that holds the root file system. The other LVs are for virtual machine disks. Everything is running fine including the virtual machines.

Here's the problem:

I need more space to work with large files on the host machine. I have extra LVM space, so I thought I'd create an LV and mount it to the host.

So I created a 500GB LV:

lvcreate -L 500G -n extra_space lvm-main

ran mkfs on it to make it an EXT4 file system:

mkfs.ext4 /dev/lvm-main/extra_space/

and mounted it at /extraroom on the host file system (fstab):

/dev/mapper/lvm--main-extra_space /extraroom ext4 errors=remount-ro 0 1

The problem is, as soon as I mount the new LV, the hard drive(s) make a chugging sound like a washing machine, cha-chug… cha-chug… cha-chug… When I unmount the LV, the noise stops. When I remount the LV, it starts chugging again.

I'm thinking there's something wrong with the way this LV is mounted that's causing the disks to move their heads a lot? This is my first time using LVM. Am I doing this wrong, or is it normal to make noise for a while when mounting a new LV to the main file system?

UPDATE:

I've run:

smartctl -t short /dev/sda

on all 4 drives which passed. I run the long version on the first two drive which also passed. I'm currently running the long version on the second two drives now (it takes several hours).

After mounting, I found a couple of interesting processes bouncing around in top. (Nothing jumped to the 'top', but I don't think i can sort top by disk io.)

One process is called "ext4lazyinit" which seems suspect to me, since the new LV is supposed to be ext4. Is it trying to format the partition as EXT4 in slow motion? Can I tell it to "get it over with!"?

There's also "sync_supers" I'm not sure what that does.

I tried Googling for "ext4lazyinit" and "sync_supers" and got mostly bug reports, nothing that explained what they do.

I'm letting it run for a while to see what happens. It's been going for about 15 so far, with no change in rhythm.