What is lvmkd and why does it slow my system down?

I am running HPUX 11.0 with HP MirrorDisk/UX and recently had a HDD failure and replaced the drive with a new one. I did a "dd" command to copy the new data to the new drive and now I have a bunch of "lvmkd" in my "ps -ef" output. These processes are gobbling up CPU time and slowing my system down. I do not want to kill the processes as I do not know what they do and "man" is no help at all.

Can anyone provide some insight on this for me?

Did you do a vgcfgrestore to reinstate the LVM configuration onto the replacement disks?
Basically it looks like your system is doing a lot of work trying to figure out what happened to its disks.
Alternatively, if you had disk mirroring on, it could be syncing up the mirrors.
You can use the vgdisplay command to list your volume group (VG) info, and lvdisplay -v to show details of each logical volume (LV).
Also, beware that if one of the replaced disks was a root mirror disk, it may not work...

lvmkd is the logical volume manager kernel daemon and I would not try to kill it, but I doubt that a kill would succeed. If your disks were mirrored, why did you use dd? The logical volume should have been intact by using the other side of the mirror. When you replaced the disk, lvm had to sync it if it was mirrored and this syncing operation is proabably was is causing your load. One other thing to try is to check for OS patches to LVM. But this does sound like a resync. I think it's lvdisplay that will show you the status of a resync.