Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
> I'm doing some testing with Ganeti, a cluster-based VM manager, which > uses DRBD as the default syncing system between nodes. My test cluster > has two nodes, Alpha & Beta. Ganeti provides a way to migrate from one > to another, handling DRBD automatically to sync to the node that isn't > running the VM. > > I'm running into an issue that I'm having difficultly understanding. > When benchmarking from within the VM, I'm getting drastically > different results depending on the node that the VM is running from. > > The DRBD benchmarks are below; ... > For comparison, I've done benchmarks with DRBD turned off. These are below; > Alpha; > Sequential Write: 206.250 MB/s ... > Beta; > Sequential Write: 207.551 MB/ As the direct write speeds look similar, I'd guess it's network related. Try turning the various optimizations off (TCP checksum offloading etc.) - if one of the machines generates bad CRCs every so many packets, it will mostly limit the data stream in the Primary => Secondary direction as that one runs much more packets.