What are dm-x devices?

[Steve]

---- Anne Wilson <cannewilson at googlemail.com> wrote: 
> What are /dev/dm-0 through to /dev/dm-3?  They are listed as block devices, 
> and owned root:disk.  Looking at gkrellm, dm-0 and dm-2 appear to mirror the 
> activity of my system disk, sdb.

They have something to do with LVM is about all I can tell you.
Hopefully you'll get a better one from somebody.

> Then there are sr0 and sr1 - what are they?  Again, I can't see much in the 
> way of a clue.
 
No idea,
Steve