I need to keep a filesystem shared between two nodes in different locations, in a way fully redundant, so that programs running in both nodes should see the whole filesystem.
The situation is that a datafile could be stored in any of the nodes, then a program running in the other could have been notified by a third party about the existence of the file, and it expects it to exist. A rsync mirroring has too much latency, even if accelerated with house-made tricks (inotify, for one). Definitely we need a shared filesystem.
Redundandy is wanted in order to be sure that we can keep going with a single node if the other datacenter becomes unreacheable.
Having only two or three nodes to share the files, probably lustre or HDFS is overkill, but it could be considered, Ceph seems too young, XtreemFS has difficulties, and DRBD sounds nice (and small) but I am afraid it could have problems to jump over high network latencies, between sites.
Am I missing some posibility? Is someone actually having this setup, sharing a filesystem across two data centers?