Dne 19.11.2011 03:35, Digimer napsal(a):
WAN/Stretch clustering suffers most for network latency. If you need to keep the data in sync across both nodes, using DRBD will limit your hard drives, effectively, to the speed and latency of the link between your nodes at the different DCs. This is rarely usable.
Stop by #linux-cluster and/or #drbd, I know there are folks there from Linbit and Hestaxo who could help you, but you're going to be facing rather expensive technical challenges. :)
DRDB over WAN is nonsense. There are many scenarios expensive/non-expensive, depends on data you want to distribute. Being you I would start with the simplest one. I can name a few: - buy netapp and create metrocluster with RRDNS - have your subnet routed into both datacenters and use virtual IPs - webapp might be somewhat static, so files might be easy to sync, as to DB data, start with master-slave replica and M/S swap, try to read data from multiple source, write to only the one - you are talking about two nodes, with your scenario only one will serve the data in time, it's not horizontal scaling, try to use both in time - have low ttl for DNS with RRDNS, add/remove records by nodes' status - don't forget about webapp side of topic, webapp must be prepared to save nonDB content - start with two nodes in one dataceter to test your horizontal scenario, you can than split it into two DC or easily add the third/fourth nodes in another DC - ....
DH