Emmanuel Noobadmin wrote, On 08/04/2010 11:33 AM:
Easier because instead of running gluster raid 0 on top of DRBD raid 1, we can take out the DRBD layer and just use gluster to achieve the equivalent by distribute on replicate.
More importantly there is the issue of cost, DRBD needs a pair of server per node for active-active. However, gluster allows me to get RAID "0.67" redundancy by "round robin" replicate.
I missed this.
i.e. If every storage node has 2 mdraid 1 block devices md0 and md1, I can mirror Server1 md0 to Server2 md1, Server2 md0 to Server3 md1 and so forth. Theoretically capable of surviving up to 50% node failure if no two adjacent node fails together. This for the cost of N+1 as compared to DRBD's Nx2 cost.
DRBD cost would still be N+1, not Nx2, if setup similarly, I think.
If Gluster is doing the mirror of "Server1 md0 to Server2..." by itself, then yes adding DRBD to it would be a bit overkill, as I would be having DRBD setup to do something similar.