Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
For the past few years we've been running VMware server on top of DRBD in normal single-primary mode. This has worked well for us, except for the pain involved in enlarging virtual disks. So we have been looking at Proxmox VE as an alternative virtualisation solution - this is nice in that it uses LVM on top of DRBD so it is quick and easy to expand a virtual disk drive. In order to facilitate migration of VMs from one peer to the other, Proxmox VE makes use of DRBD in a dual-primary configuration. This works very well, *except* in split-brain situations where both peers have running VMs and therefore both have updated their DRBD volumes. As I understand it (and I would be delighted if there is a better solution) it is necessary to discard the data on one of the peers before they can be resynchronised - which is a bit of a deal-breaker, as it appears that data loss would result. If it is not possible now, would be possible in future for a primary/primary split-brain to be resolved by keeping track of "recently updated" data on the two nodes and merge the changes rather than rolling them back on one of the nodes as in http://www.drbd.org/users-guide-emb/s-resolve-split-brain.html ? Obviously a primary/primary configuration will be anarchy unless there is coordination between peers at a higher software level - such as the Proxmox VE software which "knows" which of the peers each VM is running on. Can DRBD make use of that information to synchronise regions of a resource in different directions - or would it be possible to add that as a feature at some future date? For example, if we have LVM on top of DRBD (say /dev/drbd0), and each VM has a distinct Logical Volume for its virtual disk... VM vm1 on LV vm1data - currently running on peer A VM vm2 on LV vm2data - currently running on peer B When resolving split-brain, the region of /dev/drbd0 occupied by LV vm1data is synced from peer A to B, and the region occupied by vm2data is synced from B to A. In effect, there would be synchronisation of regions of resources rather that whole DRBD resources. In the meaintime, any more information on resolving primary/primary split-brain conditions would be very welcome. Mark _________________________________________________________________ Got more than one Hotmail account? Save time by linking them together http://clk.atdmt.com/UKM/go/186394591/direct/01/ -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.linbit.com/pipermail/drbd-user/attachments/20091127/1b15c82d/attachment.htm>