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