Sparse files and block devices

[Randy Barlow <randy@electronsweatshop.com>]

I started playing with btrfs last night, and I must say that I am very
excited! I do have one question so far. Since I was learning, I created
a sparse file, and then used mkfs to get a btrfs filesystem. I
entertained myself with that for a while, and then decided that I wanted
to try out the multi device support. I found that the device add command
requires the device to be a block device, and wouldn't accept another
sparse file that I had created. Is there a workaround, or is that just
the way it is?

I ended up just making a logical volume to get the second block device.

Thanks for making such a cool fs!