[Linux-cluster] DDRAID vs. GNBD+MD

[Gordan Bobic]

Hi,

I mentioned DDRAID in a different thread recently, but it got me 
thinking. Is there any reason why a similar solution based on GNBD plus 
standard software RAID on top wouldn't work?

Say we have 7 nodes, and we want 5+2 (RAID6 redundancy). Have each node 
export a GNBD, and then all nodes connect the said GNBDs together using 
software RAID into a /dev/md? device, and then have GFS on top of that. 
We could then lose any 2 out of the 7 nodes and still maintain 
operational status.

Would that work, or would the underlying GNBDs end up being temporarily 
out of sync sufficiently for the RAID to not be assemblable on the other 
nodes?

If this works, then that would render DDRAID redundant, except for 
performance reasons. On a related node, was DDRAID ever stabilised, or 
is it one of those perpetual alphaware projects like Coda that will 
never reach production quality due to being abandoned?

Gordan