[dm-devel] Newbie questions

[Greg Freemyer]

On Thu, 2003-11-27 at 22:46, Alec Thomas wrote:
> Hello,
> 
<snip>

> My second question is somewhat related. I am thinking about doing a
> network based block device running on device mapper. What is the "best"
> way of communicating with user-space from a device-mapper module? I
> would like to do most of the network stuff in user-space to take
> advantage of existing cluster communication infrastructure, so it would
> need to be fairly high-speed for transfer of blocks to/from user-space.
> 
Are you thinking of writing your own network based block device, or
using a pre-existing one?

There are at least 2 current ones: nbd and drbd

I have not used either, but as I understand it:

nbd handles exporting a block device, but offers no mirroring etc.

drbd is a network based mirroring solution that keeps 2 block devices in
sync.

Both of the above are kernel based implementations.  I don't know if
either works with dm.  Personally I hope that drbd and dm can be made to
work together, but I don't think anyone has tried yet.

FYI: To achieve network mirroring I believe Redhat suggests using nbd
with md.  SUSE recommends the drbd approach and has a support engineer
assigned to it.

Greg
-- 
Greg Freemyer